ELECTRO-TECHNICAL 
SERIES 


REESE   LIBRARY 


__n__n__n__ rt, 


UNIVERSITY  OF  CALIFORNIA. 

^ecerceJ  &CA.     /  £~,  ,  180  &  . 

'•cessions  No.  &i  00 1-  .      CA/.s-.s-  No. 


BY  THE  SAME  AUTHORS 

Elementary  Electro  -  Technical  Series 

COMPRISING 

Alternating  Electric  Currents. 
Electric  Heating. 

Electromagnetism. 

Electricity  in  Electro-Therapeutics. 

Electric  Arc  Lighting. 
Electric  Incandescent  Lighting. 
Electric  Motors. 

Electric  Street  Railways. 
Electric  Telephony. 

Electric  Telegraphy. 

Cloth,        Price  per  Volume,        $1.00. 


Electro-Dynamic  Machinery. 
Cloth,  $2.50. 


THE  W.  J.  JOHNSTON  COMPANY 

253  BROADWAY,  NEW  YORK 


ELEMENTARY  ELECTRO-TECHNICAL  SERIES 

ELECTRIC    STREET 
RAILWAYS 


BY 

EDWIN  J.  HOUSTON,  PH.  D. 

AND 

A.  E.  KEffN^LLY,  So.  D. 


NEW  YORK 

THE  W.  J.  JOHNSTON  COMPANY 

253  BROADWAY 

1896 


VI  PREFACE. 

clear  conception  of  its  method  of  oper- 
ation. The  authors  have  prepared  this 
little  volume  of  the  Mectro- Technical  Series 
in  the  belief  that  these  difficulties  are  ap- 
parent rather  than  real — that  it  is  quite 
possible  for  the  general  public  to  obtain  a 
fairly  intimate  knowledge  of  the  leading 
principles  of  electric  traction  without  any 
previous  knowledge  of  electrotechnics. 

It  is  a  matter  of  nece'ssity  rather  than 
choice,  at  the  close  of  this  nineteenth  cen- 
tury, when  electric  traction  has  become  so 
nearly  universal,  that  a  knowledge  of  the 
main  principles  concerned  should  be  gener- 
ally accessible,  without  special  training, 
and  more  especially  is  this  desirable  on  the 
part  of  those,  now  an  exceedingly  exten- 
sive class,  wrho  are  connected  in  some  way 
or  other  with  such  enterprises. 

The  authors  present  this  book  to  the 
general  public  hoping  that  it  will  meet  the 
need  above  referred  to. 


(UNIVERSITY 


CONTENTS. 


I.     INTRODUCTION,         ....  1 
II.     EARLY  HISTORY  OF  THE  ELECTRIC 

RAILWAY,            ....  8 

III.  ELEMENTARY  ELECTRIC  PRINCIPLES,  15 

IV.  THE  MOTOR, 67 

V.     CARS  AND  CAR  TRUCKS,           .         .  97 

VI.     ELECTRIC   LIGHTING  AND  HEATING 

OF  CARS,     .....  134 

VII.     CONTROLLERS  AND  SWITCHES,          .  154 

VIII.     TROLLEYS, 204 

IX.     TROLLEY  LINE  CONSTRUCTION,         .-  219 

X.     TRACK  CONSTRUCTION,     .         .         .  242 
iii 


IV  CONTENTS. 

CHAPTER  PAGE 

XL  ELECTEOLYSIS,          ....  249 

XII.  SWITCHBOARDS,         ....  262 

XIII.  GENERATORS  AND  POWER  HOUSES,  279 

XIV.  OPERATION  AND  MAINTENANCE,       .  297 
XV.  STORAGE  BATTERY  SYSTEM,     .         .  307 

XVI.  ELECTRIC  LOCOMOTIVES,           .         .  323 


ELECTRIC  STREET  RAIL- 
WAYS. 

CHAPTER  I. 

INT  KODUCTION. 

THE  introduction  of  the  electric  street 
railway  naturally  caused  much  wonder- 
ment. There  seemed  at  the  first  some- 
thing weird  in  the  possibility  of  propel- 
ling a  heavily  loaded  vehicle,  from  place  to 
place,  without  any  apparent  motive  power, 
and,  even  at  the  present  time,  there  remains 
no  little  astonishment  in  the  mind  of  the 
casual  observer  as  to  how  the  electric 
agency  can  silently,  yet  surely,  find  its  way 
from  a  power  house,  in  some  remote  corner 
of  a  city,  through  an  intricate  maze  of 


2  ELECTRIC    STREET   RAILWAYS. 

streets  and  turnings,  and  propel  eacli  car 
as  though  the  latter  were  under  the  guid- 
ance of  a  familiar  spirit.  The  wonder 
grows,  when  it  is  pointed  out  that  the 
electric  current  not  only  has  to  find  its 
way  from  the  power  house  over  the 
trolley  wires  to  the  cars,  wherever  these 
may  be,  but  has  also  to  return  to  the 
power  house  through  the  track  and 
ground. 

It  is,  unfortunately,  too  true  that  the 
real  nature  of  electricity  remains  un- 
known, even  in  this  electric  age.  For  this 
reason,  there  has,  perhaps,  existed,  in  the 
minds  of  the  public,  too  marked  an  unwill- 
ingness to  attempt  even  to  form  ideas  as 
to  the  laws  which  control  electric  opera- 
tions. But  it  should  not  be  forgotten, 
that  although  our  knowledge  of  the  exact 
nature  of  electricity  is  imperfect,  yet 


INTRODUCTION.  3 

our  knowledge  of  the  manner  in  which  it 
operates,  that  is  of  the  laws  which  control 
it,  is  surprisingly  definite.  Indeed,  so  far 
as  the  laws  which  govern  the  flow  of 
electric  currents  through  conducting  paths 
or  circuits  are  concerned,  our  knowledge 
is  even  more  definite  than  of  the  laws 
which  control  the  flow  of  water  or  gas 
through  pipes.  In  fact,  as  we  shall 
subsequently  see,  a  remarkable  analogy 
exists  between  the  laws  which  govern  the 
flow  of  gross  matter  in  the  fluid  state,  that 
is  as  liquids  or  gases,  and  the  lawTs  which 
govern  the  flmv  of  electricity. 

It  may  be  well,  therefore,  before  pro- 
ceeding further  with  the  general  discus- 
sion of  electric  street  railways,  to  outline 
briefly  the  points  of  similarity  between 
the  flow  of  liquids  and  the  flow  of  elec- 
tricity. 


4  ELECTRIC    STREET   RAILWAYS. 

Perhaps  no  better  illustration  could  be 
given,  concerning  some  of  the  laws  of 
liquid  flow,  than  that  taken  from  the  dis- 
tribution of  water  through  the  mains  and 
pipes  of  a  large  city.  Here,  as  is  well 
known,  a  supply  of  water  is  provided  in 
a  reservoir,  at  a  high  level  or  pressure. 
Pipes  or  mains  connecting  with  this  reser- 
voir extend  beneath  the  streets  to  all  por- 
tions of  the  city  that  are  to  be  supplied 
with  water.  No  difficulty  will  be  experi- 
enced in  understanding  how,  if  no  obstruc- 
tion exists  in  the  pipes,  the  water  will 
flow  through  them  from  the  reservoir  and 

escape  through  any  outlet  at  a  lower  level. 

" 

Let  us  now  examine  the  network  of 
pipes  connected  with  a  reservoir  in  a 
system  of  municipal  water  distribution. 
It  is  evident  that  the  object  of  such  a 
system  is  to  supply  the  houses  or  other 


INTRODUCTION.  5 

buildings  either  with  water,  or  with  the 
power  the  water  is  capable  of  exerting. 
For  this  purpose  two  sets  of  pipes  are 
provided ;  viz., 

(1)  Those  connected  immediately  with  the 
reservoir  and  intended  to  carry  the  water. 

(2)  Those  connected  to  the  consumers' 
waste  pipes. 

The  latter  are  connected  intermediately 
with  the  sew^er  system,  and  ultimately 
with  the  lake,  river,  or  ocean  into  which 
such  sewer  system  discharges. 

Between  the  reservoir  and  the  river,  it 
is  evident  that  the  flow  of  water  through 
the  pipes  is  due  to  gravity,  the  water  find- 
ing its  way  through  the  pipes  in  obedience 
to  the  law  of  liquid  levels.  After  the 
river  has  been  reached,  and  the  water  is 
ultimately  discharged  into  the  ocean,  thus 
reaching  its  lowest  level,  some  means  must 


6  ELECTRIC    STREET    RAILWAYS. 

be  provided  for  causing  the  water  to  rise 
against  the  force  of  gravity  and  fill  the 
reservoir  afresh.  This  energy  is  received 
from  the  sun  during  the  evaporation  of 
the  water  when  it  passes  into  vapor  and 
rises  into  the  atmosphere.  On  the  loss  of 
the  heat  so  received  the  water  again  falls 
under  the  influence  of  gravity,  and  returns 
to  the  reservoir. 

An  analogy  between  the  preceding 
system  of  water  distribution  through  the 
pipes  of  a  city,  and  a  system  of  electric 
distribution  through  the  trolley  wires,  is 
evident.  Here,  as  we  shall  more  fully  see 
in  a  subsequent  chapter,  an  actual  differ- 
ence of  electric  level  exists,  whereby  an 
electric  source,  or  generator,  at  the  power 
house,  causes  the  electricity  to  flow 
througl;  all  the  conducting  outgoing  trol- 
ley wires  from  the  higher  electric  level 


INTRODUCTION.  7 

of  the  generator  to  the  cars.  In  passing 
through  the  cars,  it  may  light  and  heat 
them  as  well  as  drive  their  motors.  On 
leaving  the  cars  it  flows  through  the 
ground  back  again  to  the  generators  in  the 
power  house.  In  this  latter  part  of  its  cir- 
cuit or  path,  an  analogy  is  to  be  found 
between  the  discharge  of  the  water  to 
the  lower  level  of  the  ocean,  prior  to 
its  passage  back  again  to  the  higher  level 
of  the  reservoir. 

Although  we  have  thus  traced  the  anal- 
ogy between  liquid  flow  and  electric  flow, 
and  have  shown  that  the  same  general 
laws  apply  to  each,  yet  it  must  be  remem- 
bered that  this  is  an  analogy  only ;  and 
that  electricity  is  not  believed  to  be  a  mate- 
rial fluid.  The  analogy  is,  however,  useful, 
and  will  aid  the  student  in  forming  practi- 
cal conceptions  of  the  electric  circuit. 


CHAPTER  II. 

EARLY    HISTORY    OF  THE    ELECTRIC   RAILWAY. 

THE  broad  idea  of  propelling  vehicles 
by  means  of  the  electric  current  appears  to 
have  suggested  itself  to  the  minds  of 
inventors  at  an  early  date.  As  long  ago  as 
1835,  Thomas  Davenport,  of  Vermont,  con- 
structed a  working  model  of  a  car  pro- 
pelled by  an  electric  motor  of  his  own 
invention.  In  1838,  Robert  Davidson,  of 
Scotland,  also  produced  an  electrically  pro- 
pelled car.  Both  of  these  early  cars 
derived  their  propelling  current  from 
voltaic  batteries  carried  on  the  car. 

The  idea  of  taking  the  electric  current 
required  for  the  propulsion  of  the  car  from 

8 


HISTORY.  OF   THE   ELECTRIC    RAILWAY.         9 

conductors  laid  alongside  the  track  was 
not  conceived  until  a  somewhat  later  date ; 
namely,  in  1840,  when  Henry  Pinkus 
obtained  letters  patent  in  Great  Britain  for 
a  method  of  propelling  carriages  either  on 
railroads  or  on  ordinary  highways.  This 
patent  discloses  among  other  things,  the 
broad  idea  of  taking  electric  current  from 
conductors,  in  contradistinction  to  employ- 
ing batteries  on  the  car. 

Space  will  not  permit  us  to  enter  in 
detail  on  this  portion  of  the  early  history 
of  the  electric  railway.  It  will  suffice  to 
say,  that  in  1851,  Professor  Page  of  the 
Smithsonian  Institution  devised  an  electric 
locomotive  which  he  ran  on  a  track  at  the 
rate  of  nineteen  miles  an  hour.  This 
locomotive,  like  those  of  Davenport  and 
Davidson,  carried  the  voltaic  battery 
required  for  its  propulsion.  About  the 


10  ELECTRIC   STREET   RAILWAYS. 

same  time  Professor  Moses  G.  Farmer  also 
devised  an  electrically  propelled  car. 

All  these  early  discoveries  belong  to  the 
type  of  ideas  that  are  born  too  early  to 
come  to  fruition.  Practically  the  only 
electric  source  that  was  known  at  this  date 
was  the  voltaic  battery,  which  is  incapable 
of  commercially  producing  the  powerful 
electric  currents  required  for  the  propul- 
sion of  street  cars.  It  was  not  until  the 
dynamo-electric  machine  was  perfected 
that  electric  car  propulsion  became  com- 
mercially practicable. 

The  advent  of  the  dynamo-electric 
generator,  therefore,  marked  the  second  era 
in  the  history  of  electric  railway  develop- 
ment. The  low  cost  at  which  this  elec- 
tric source  can  furnish  powerful  currents 
attracted  the  attention  of  inventors,  who 


HISTORY    OF  THE   ELECTRIC    RAILWAY.       11 

long  before  had  recognized  the  part  elec- 
tric! fcy  was  destined  to  play  in  electric 
locomotion.  Consequently,  this  era  of  the 
history  of  the  electric  railway  contains 
many  inventions. 

It  is  not  our  intention  to  enter  into  any 
discussion  as  to  the  claims  of  the  various 
inventors  to  priority  in  any  of  the  more 
salient  features  of  the  art  of  electric  trac- 
tion. We  will  content  ourselves  with  a 
brief  account  only  of  some  of  the  work 
accomplished  at  this  time. 

One  of  the  pioneers  at  the  beginning  of 
this  era  in  the  history  of  the  electric  rail- 
way was  George  Green,  who  devised  a 
road  on  a  plan  similar  to  that  of  Farmer, 
but  containing  many  marked  improve- 
ments. Green,  who  was  poor,  experienced 
difficulty  in  getting  his  patent  interests 


12  ELECTRIC    STREET   RAILWAYS. 

attended  to.  Being  placed  in  interferences 
with,  other  applicants,  a  patent  was  not 
issued  to  him  until  the  last  month  of  1891, 
although  applied  for  as  early  as  1879. 

Passing  by  a  number  of  inventors  who 
devised  electric  locomotives  of  various 
types,  we  come  to  the  electric  railway  of 
Siemens  and  Halske,  which  was  put  into 
actual  operation  at  the  Industrial  Exhibi- 
tion of  Berlin  in  1879.  As  in  all  electric 
railways  belonging  to  this  era,  the  motive 
power  was  derived  from  dynamos  located 
at  a  central  station.  The  current  was 
delivered  to  the  motor  by  means  of  a  slid- 
ing contact  under  the  locomotive,  rubbing 
against  a  rail  placed  midway  between  the 
two  track  rails. 

Very  little  was  done  in  electric  railways 
in  the  United  States,  prior  to  1883.  It  is 


HISTORY   OF   THE   ELECTRIC   RAILWAY.      13 

true  that  in  1880  some  work  was  under- 
taken by  Edison  which  resulted  in  the 
erection  of  an  experimental  track,  and  that 
prior  to  this  date ;  namely,  in  May,  1879, 
Stephen  D.  Field  had  done  some  experi- 
mental work  which  he  protected  in  the 
United  States  Patent  office  by  a  caveat. 

In  the  meantime  inventors  in  other 
countries  had  by  no  means  been  idle. 
The  honor  of  establishing  the  first  com- 
mercial electric  street  railway  appears  to 
belong  to  Germany,  where  the  Lichten- 
feld  line  was  put  in  operation  in  1881. 
Another  road  was  opened  at  Portrush,  in 
the  north  of  Ireland,  in  1883,  the  dynamos 
being  in  this  case  driven  by  water  power. 

Among  early  railways  operated  in  the 
United  States  was  one  constructed  and 
put  in  operation  by  Vanderpoele,  at  the 


14  ELECTRIC    STREET   RAILWAYS. 

Chicago  State  Fair  during  two  months 
in  1884.  A  short  line,  located  on  one 
of  the  piers  on  Coney  Island,  N.  Y.,  was 
operated  during  the  summer  season  of 
1884.  The  year  1884  also  saw  the  first 
public  electric  street  railway  in  operation 
at  Providence,  R.  L,  and  the  first  practical 
trolley  road  was  that  in  the  suburbs  of 
Kansas  City,  Mo.,  in  the  same  year. 

The  advantages  possessed  by  electric 
traction  over  ordinary  methods,  such  for 
example,  as  horse  cars,  are  so  great,  that 
while  in  1884  the  first  electric  road  was 
installed  in  the  United  States,  there  were, 
in 

1889,  50  roads  with   100  miles  of  track. 

1890,  200  "  1,200  " 

1891,  275  "  2,250  " 
1894,  606  "  7,470  " 
1895  (July),  880  "  10,863  " 


€IVERSITY) 
w  .X 


CHAPTER  III. 

ELEMENTARY  ELECTRIC  PRINCIPLES. 

BEFORE  proceeding  to  a  consideration  of 
purely  electrical  matters  it  will  be  advis- 
able to  discuss  briefly  the  general  subjects 
of  work  and  activity.  Suppose,  for 
example,  that  a  street  car  is  being  drawn 
at  a  steady  rate  of  5  miles  an  hour  by 
a  horse  along  a  level  track.  Then  it  is 
evident  that  the  horse  has  to  do  work  in  a 
mechanical  sense,  in  order  to  maintain  the 
motion.  If  the  car  could  be  so  constructed 
that  there  was  absolutely  no  friction  in  its 
journal  bearings,  and,  moreover,  if  the  road- 
bed could  be  so  constructed  that  there 
were  no  inequalities  in  its  metal  surfaces, 

15 


16  ELECTRIC   STKEET    RAILWAYS. 

and  no  friction  between  the  wheels  and 
the  rails,  then  no  work  would  have  to  be 
expended  in  maintaining  a  steady  speed 
on  a  level  road;  or,  in  other  words,  once 
the  car  was  set  in  motion,  it  would  con- 
tinue to  run  at  the  same  rate  for  an  indefi- 
nite period.  Under  practical  conditions, 
however,  as  is  well  known,  a  certain 
amount  of  friction  necessarily  occurs  and 
has  to  be  overcome.  The  greater  this 
friction  the  greater  will  be  the  amount  of 
work  which  must  be  expended  in  order  to 
keep  the  car  running.  If  the  road  instead 
of  being  level  is  on  a  gradient,  then  it  is 
evident  that  an  ascent  of  this  gradient 
necessitates  the  expenditure  of  work 
against  gravitational  force,  in  addition  to 
the  work  expended  in  overcoming  friction. 
The  heavier  the  car  and  the  greater  its 
load ;  i.  e.,  the  greater  the  number  of  pas- 
sengers it  carries,  the  greater  will  be  the 


ELEMENTARY    ELECTRIC    PRINCIPLES.       17 

frictional  work  and  also  the  gravitational 
work. 


In  order  to  estimate  the  amount  of 
work  done  in  any  particular  case,  as  for 
example,  in  the  case  above  referred  to  of  a 
moving  car,  reference  is  had  to  certain 
units  of  work.  It  is  evident  that  when 
the  car  is  being  pulled  by  a  rope,  the  rope 
is  subjected  to  tension,  such  as  might  be 
produced  by  a  weight  supported  over  a 
pulley.  The  harder  the  horse  pulls,  the 
greater  will  be  the  tension  and  the  greater 
the  equivalent  weight.  Thus  a  horse  may 
readily  exert  a  pull  upon  its  traces  of 
400  pounds  weight.  The  greater  the  dis- 
tance through  which  the  tension  is  ex- 
erted, the  greater  will  be  the  work  done. 
Thus  if  a  tension  of  400  pounds  weight 
be  steadily  exerted  upon  a  car  so  as  to 
draw  the  latter  through  a  distance  of 


18  ELECTRIC    STREET    RAILWAYS. 

100  feet,  then  the  work  done  will  be  100 
times  as  great  as  if  the  car  were  only 
drawn  under  this  tension  through  1  foot; 
and,  generally,  the  amount  of  work,  which 
is  performed  by  a  tension  or  pull,  is  equal 
to  the  tension  multiplied  by  the  distance 
through  which  it  has  been  exerted,  so  that 
if  the  horse  continues  to  exert  a  pull  of 
400  pounds  so  as  to  draw  the  car  100 
feet,  the  horse  will  have  expended  on 
the  car  an  amount  of  work  equal  to 
400  X  100  =  40,000  foot-pounds. 

The  foot-pound  is  not  generally  em- 
ployed as  the  unit  of  work,  e'xcept  in 
English-speaking  countries,  and,  even  in 
such  countries,  scientific  men  generally 
prefer  the  joule,  a  unit  based  on  the 
French  system  of  weights  and  measures. 

/TOO 

A  joule  is  of  a  foot-pound,  approxi- 


ELEMENTARY   ELECTRIC    PRINCIPLES.       19 

mately ;  or,  one  foot-pound  may  be  taken 
as  equal  to  1.355  joules.  The  foot-pound 
is,  consequently,  roughly  one-third  greater 
than  the  joule.  If  we  multiply  the 
number  of  foot-pounds  by  1.355,  we 
obtain  the  number  of  joules  within  a 
degree  of  accuracy  sufficient  for  all  ordi- 
nary purposes.  For  example,  when  a 
man,  weighing  150  pounds,  raises  himself 
through  a  vertical  distance  of  100  feet,  he 
performs  an  amount  of  work  equal  to 
100  x  150  =  15,000  foot-pounds  in  the 
process.  The  same  amount  of  work  might 
be  expressed  in  joules  instead  of  in  foot- 
pounds by  multiplying  the  number  of 
foot-pounds  by  1.355;  or,  15,000  x 
1.355  =  20,325  joules.  Again,  when  the 
horse  raises  a  25,000  pound  car  along  a 
gradient  through  a  total  vertical  distance 
of  100  feet,  it  thereby  necessarily  per- 
forms an  amount  of  work  against  gravi- 


20  ELECTRIC    STREET   RAILWAYS. 

tation,  represented  by  100  X  25,000  — 
2,500,000  foot-pounds.  This  amount  of 
work  might  be  expressed  in  joules  by 
multiplying  by  1.355  =  3,387,500  joules. 

A  very  important  distinction  must  be 
carefully  kept  in  mind  between  work 
expended  in  performing  any  operation, 
and  the  rate  at  which  that  work  is  ex- 
pended;  or,  as  it  is  usually  called,  the  activ- 
ity. For  example,  a  man  weighing  150 
pounds  may  raise  his  weight  through  100 
feet,  by  ascending  a  flight  of  stairs,  in  10 
minutes,  or  in  1  minute.  The  amount 
of  work  done  against  gravitation  will  in 
either  case  be  the  same ;  namely,  15,000 
foot-pounds,  or  20,325  joules,  but  it  is  evi- 
dent that  the  effort  which  the  man  must 
exert  in  the  two  cases,  and  the  relative 
degree  of  exhaustion  which  he  will 
undergo  will  be  very  different.  Ascend- 


ELEMENTARY   ELECTRIC   PRINCIPLES.      21 

ing  the  flight  in  10  minutes  would  be 
walking  upstairs  at  a  leisurely  rate,  while 
ascending  it  iu  1  minute  would  mean 
running  upstairs  at  nearly  full  speed. 
The  man  is  obviously  ten  times  more 
active  in  the  second  case  than  in  the  first  ; 
or,  he  expends  energy  ten  times  faster. 
In  other  words,  he  works  ten  times  as  fast 
in  the  second  case  as  in  the  first.  Conse- 
quently, activity  may  be  defined  as  the 
rate-of-working. 

The  unit  of  activity  generally  employed 
in  English-speaking  countries  is  that  based 
on  the  foot-pound,  and  is  \X\zfoot-pound-per 
second,  so  that  unit  activity  is  the  rate 
of  expending  1  foot  pound  of  work  in  1 
second.  If,  for  example,  a  man  raises  his 

weight  of  1  50  pounds  through  -r^th  of  a 


foot  in  each  second  of  time,  he  expends  an 


22  ELECTKIC    STREET    RAILWAYS. 

amount  of  work  equal  to  150  X  -—  =  1 

150 

foot-pound  in  each  second ;  or,  is  working 
at  the  unit  rate,  or  with  the  unit  activity. 
As  this  rate  of  working  would  evidently 
be  a  very  small  one,  in  dealing  with  large 
machines  it  is  more  usual  to  employ  a 
unit  called  the  horse-power,  which  is  550 
foot-pounds  in  1  second.  Thus,  when  a 
man  weighing  150  pounds,  raises  his 
weight  through  100  feet  in  1  minute  or  60 
seconds,  he  will  perform  15,000  foot-pounds 
in  60  seconds,  or  he  will  average  a  rate 

of   working   of  -  =  250   foot-pounds 

250         5   . 
per  second;  or,  — —  ==  — jths  horse-power  ; 

or,  will  be  working  roughly  at  half  the 
rate  of  a  standard  horse.  If,  however,  the 
man  ascends  100  feet  in  10  minutes,  he 
performs  15,000  foot-pounds  in  600  sec- 


ELEMENTARY   ELECTRIC    PRINCIPLES.      23 

onds;   or,  at  an   average  rate  of  25  foot- 
pounds-per-second,  that  is  his  activity  is 

only  -^—  =  Truths  of  one  horse-power. 

OOU 


Where  the  joule  is  employed  as  the 
unit  of  work,  the  international  unit  of 
activity  is  the  joule-per-second ;  or,  as  it 
is  commonly  called,  the  watt,  after  James 
Watt.  It  is  an  interesting  fact  that  James 
Watt  introduced  the  term  horse-power  in 
connection  with  his  early  steam  engine, 
and,  in  accordance  with  international 
usage,  of  naming  practical  units  after  the 
names  of  distinguished  scientists,  Watt's 
name  has  been  selected  in  connection  with 
the  international  unit  of  activity.  An 
activity  of  1  foot-pound  per  second  is 
an  activity  of  1.355  joules-per-second  or 
1.355  watts.  Similarly,  an  activity  of  1 
horse-power,  or  550  foot-pounds-per-sec- 


OF  THE 

TJNI^  ERSITT 


24  ELECTRIC    STREET    RAILWAYS. 

ond,  is  an  activity  of  550  X  1.355  —  746 
joules-per-second,  or  746  watts.  If  we 
multiply  the  number  of  horse-power 
which  are  being  developed  in  any  machine 
by  746,  we  obtain  the  activity  of  that 
machine  expressed  in  watts.  As  the  rate 
of  0.738  foot-pound  -per-second  is  a  very 
small  unit,  being  about  26  per  cent,  smaller 
than  the  foot-pound  per  second,  and 
requiring,  therefore,  large  numbers  to 
express  large  powers,  in  dealing  with 
engines,  it  is  customary  to  use  a  deci- 
mal multiple  of  this  unit,  so  that  the 
practical  international  unit  of  activity 
is  the  kilowatt,  or  1,000  watts.  Conse- 
quently, the  horse-power,  being  as  above 

746 
mentioned  746  watts,  is     r-ths   °f 


larger  unit,  or  the  kilowatt,  and  may  be 
taken  as,  approximately,  3/4ths  of  a  kilo- 
watt. A  kilowatt  will,  therefore,  be  4/3rds 


ELEMENTARY   ELECTRIC   PRINCIPLES.      25 

or  1  l/3rd  horse-power,  approximately. 
When  we  speak  of  a  dynamo  or  motor 
as  having  a  capacity  of  100  kilowatts,  (that 
is  to  say  of  being  capable  of  maintaining 
an  activity  of  100  kilowatts,  or  100,000 
watts  =  100,000  joules-per-second  =  73,800 
foot-pounds -per-second,)  we  mean  an 
activity  of  1  1/3  x  100  =  133  horse- 
power, approximately ;  or,  134  horse-power 
more  nearly. 

The  problem  which  presents  itself  to 
the  street  railway  manager  is  that  of 
economically  driving  street  cars  by  electric 
power,  and  it  is  to  be  carefully  remem- 
bered that  the  same  amount  of  power 
must  be  exerted  by  the  engines  in  the 
power  house  as  by  horses  drawing  the 
cars  along  the  streets  at  the  same  rate.  In 
fact  the  engines  in  the  power  house  will 
have  to  work  harder,  or  develop  a  greater 


26  ELECTRIC    STREET   RAILWAYS. 

activity  than  the  horses,  owing  to  the 
necessary  losses  of  power  which  inci- 
dentally occur  in  transmission.  If,  for 
example,  we  imagine  that  all  the  cars  in 
the  streets  of  the  city  are  travelling  steadily 
along  at  the  same  average  rate  as  the  pis- 
tons of  the  engines  in  the  power  house,  then 
the  pull  exerted  by  the  pistons  will  be 
equal  to  the  aggregate  equivalent  pull  of 
all  the  cars,  increased  by  a  certain  amount 
corresponding  to  losses  in  transmission. 

It  remains  now  to  show  how  power  can 
be  calculated  and  expressed  in  electric 
units.  In  other  words,  if  we  require  to 
supply  a  certain  activity  in  horse-power  or 
kilowatts  to  a  moving  car,  we  need  to  find 
how  to  express  this  power  in  relation  to 
electric  circuits,  since  the  power  must  be 
conveyed  by  the  electric  circuits  from  the 
power  house  to  the  car.  We  will,  there- 


ELEMENTARY    ELECTRIC    PRINCIPLES.      27 

fore,  discuss  the  elementary  principles  of 
electric  circuits. 

An  electric  circuit  is  a  conducting  path 
provided  for  the  passage  of  electricity.  It 
connects  an  electric  source  or  generator, 
with  the  devices  to  be  operated  by  the 
electric  current.  Such  a  circuit  is  said  to 
be  made  or  closed  when  its  path  is  com- 
pleted, and  is  said  to  be  broken  or  opened 
when  its  path  is  interrupted  at  some  point 
or  points.  Thus,  in  the  case  of  the  elec- 
tric car,  an  electric  circuit  exists  between 
the  power  house  where  the  current  is 
generated,  through  the  trolley  wire  and 
track,  to  the  motors  of  the  car.  When 
such  a  circuit  is  closed,  the  current  passes 
through  the  car,  and  drives  the  motor  or 
motors.  On  the  contrary,  when  the  circuit 
is  opened  by  the  motor  man  at  the  switch, 
the  current  ceases  to  flow. 


28  ELECTRIC   STREET    RAILWAYS. 

Fig.  1,  represents  a  simple  electric  cir- 
cuit consisting  of  a  generator  G,  a  trolley 
wire  W  W ,  a  car  with  its  trolley 
Tj  motors  m  m,  and  the  track  K  K, 
employed  as  a  return  conductor.  What 
passes  through  this  circuit  is  an  electric 
flow,  generally  called  an  electric  current. 

W  >          W 


£ 

FIG.  1.— SIMPLE  CAB  CIRCUIT. 


In  order  to  obtain  definite  ideas  concern- 
ing an  electric  current,  a  unit  of  electric 
current,  or  rate-of-flow,  called  an  ampere,  is 
employed.  It  will  be  advisable,  however, 
before  discussing  the  value  of  the  ampere, 
to  consider  certain  other  quantities  which 
are  always  intimately  connected  with 
every  electric  circuit.  Turning  our  atten- 


ELEMENTARY   ELECTRIC   PRINCIPLES.      29 

tion  first  to  the  generator  G,  it  is  necessary 
to  observe  that  the  primary  function  of 
the  generator  is  not,  as  is  ordinarily 
believed,  to  produce  electric  current,  but 
to  produce  in  the  circuit  a  variety  of  force, 
called  electromotive  force,  which  is  gener- 
ally abbreviated  E.  M.  F.  When  the 
generator  is  driven  by  an  engine  it  will 
supply  an  E.  M.  F.  whether  the  electric 
circuit  is  open  or  closed,  that  is  to  say, 
whether  an  electric  current  can  or  cannot 
flow  in  the  circuit.  In  other  words,  the 
generator,  when  running,  always  supplies 
E.  M.  F.,  but  no  current  can  be  sent 
through  the  circuit  until  the  circuit  is 
closed.  This  corresponds  to  the  case  of  a 
reservoir,  which  produces  a  water  pressure 
whether  the  water  be  escaping  under  that 
pressure  or  not. 

In  Fig.  2,  a  rotary  pump  P,  is  supposed 


30  ELECTRIC    STREET   RAILWAYS. 

to  be  placed  in  a  power  house  situated  by 
the  side  of  a  river  K  K,  and  provided  with 
a  pipe  by  which  it  can  draw  water  from  the 
river  and  send  it  through  the  pipe  W  W. 
M  is  a  water  motor  situated  at  some  con- 


w 


K| 
FIG.  2. — SIMPLE  WATER  CIRCUIT. 


venient  point  and  connected  with  the 
main  pipe  W  W,  by  a  small  branch  pipe, 
in  which  is  placed  a  valve  V.  When  the 
valve  is  closed,  the  motor  M,  is  prevented 
from  running,  since  no  water  current 
passes  through  it.  The  hydraulic  circuit 
W  W,  K  J£7  may  then  be  said  to  be  broken 


ELEMENTARY   ELECTRIC    PRINCIPLES.      31 

or  open.  When,  however,  the  valve  V,  is 
opened,  water  passes  through  the  motor 
Mj  and  discharges  into  the  river,  thus  clos- 
ing the  hydraulic  circuit,  and  permitting  a 
water  current  to  flow  through  the  circuit. 
It  is  evident  that  whether  the  valve  F,  be 
opened  or  not,  the  generator  or  water 
pump  P,  will  develop,  when  running,  a 
pressure  or  watermotive  force  in  the  pipe 
W  W,  but  that  no  current  or  flow  of  water 
can  take  place  until  the  valve  F,  permits 
it  to  do  so,  thus  closing  the  circuit.  Here 
the  watermotive  force,  produced  by  the 
action  of  the  pump  whether  the  hydraulic 
circuit  be  opened  or  closed,  corresponds  to 
the  electromotive  force  produced  by  the 
generator  whether  the  electric  circuit  be 
opened  or  closed. 

The  pressure  generated  in   the  supply 
pipe     W  W,  by   the    pump   P,    might  be 


32  ELECTRIC   STREET   RAILWAYS. 

expressed  in  pounds-per-square-inch  ;  or,  as 
the  pressure  produced  by  a  column  of 
water  a  certain  number  of  feet  in  height. 
In  the  electric  circuit  the  pressure  pro- 
duced by  the  action  of  the  generator  6r,  is 
expressed  in  units  of  electromotive  force, 
called  volts.  In  street-car  systems  the  elec- 
tric pressure  produced  by  the  generator  is 
almost  invariably  about  500  volts ;  that  is 
to  say,  the  pressure  between  the  trolley 
wires  and  the  track  is  maintained,  approxi- 
mately, at  500  volts,  while  the  pressure  at 
the  power  house  between  the  terminals  of 
the  generator  6r,  may  be  somewhat  in 
excess  of  this,  say  550  volts,  in  order  to 
make  up  for  the  loss  of  pressure  occurring 
in  the  circuit. 

If  a  reservoir  R,  Fig.  3,  filled  with  water 
and  maintained  at  a  constant  level  L  L,  be 
allowed  to  discharge  steadily  through  two 


ELEMENTARY    ELECTRIC   PRINCIPLES.       33 

pipes,  as  indicated  in  Fig.  3,  one  pipe  A  !>, 
being  a  long,  narrow  pipe,  and  the  other 
C  D,  being  a  short,  wide  pipe,  it  is  evident 
that  a  much  greater  flow  of  water  will 
take  place  in  a  given  time  through  the 
pipe  O  Dj  than  through  the  pipe  A  £, 
since  the  water  pressure  at  the  openings  A 


I 


FIG.  3. — RESISTANCE  OF  WATER  PIPES. 

and  Cj  is  the  same ;  namely,  the  height  of 
water  in  the  reservoir.  The  difference  in 
the  rat e-of -flow  of  water  may  be  ascribed 
to  the  different  resistance  offered  by  the 
two  pipes  to  the  flow  of  water,  the  resist- 
ance of  the  long,  narrow  pipe  being  com- 
paratively great,  and  that  of  the  short, 
wide  pipe  being  comparatively  small. 


34  ELECTRIC    STREET    RAILWAYS. 

In  the  same  way,  Fig.  4,  represents  an 
electric  generator  6r,  which,  when  running, 

O  /  O' 

acts  the  part  of  the  reservoir  in  the  pre- 
ceding case,  since  it  supplies  a  steady  elec- 
tric pressure  between  its  terminals.  If 
two  circuits  are  closed  to  this  pressure,  one 
through  a  long,  thin  wire  A  A'  B  B,  and 


B1 
FIG.  4. — RESISTANCE  OP  CONDUCTING  WIRES. 

the  other,  through  a  short,  thick  wire  O  C' 
D1  D,  then  the  electric  flow  or  current, 
which  will  pass  through  these  two  circuits, 
will  be  very  different,  a  comparatively 
small  or  feeble  current  passing  through 
the  long,  fine-wire  circuit,  and  a  compara- 
tively strong,  or  heavy  current,  passing 
through  the  short  thick- wire  circuit. 


ELEMENTARY    ELECTRIC    PRINCIPLES.       35 

This  difference  in  flow  or  current  be- 
tween the  two  circuits  may  be  ascribed  to 
a  difference  in  what  is  called  their  electric 
resistance.  The  electric  resistance  of  a 
long,  thin-  wire  circuit  is  comparatively 
great  ;  i.  e.,  it  offers  a  comparatively  great 
obstacle  to  the  passage  of  electricity  under 
the  pressure  of  the  generator  G  ;  while  a 
short,  thick-wire  circuit  has  a  compara- 
tively small  electric  resistance;  i.  e.,  it 
offers  a  lesser  obstacle  to  the  passage  of 
electricity. 

Electric  resistance  is  usually  measured 
in  terms  of  a  unit  of  resistance  called  the 
ohm,  after  Dr.  Ohm  of  Berlin,  who  first 
pointed  out  the  laws  regulating  the  flow 
of  electricity  in  conducting  circuits.  The 
amount  of  resistance  ;  i.  e.,  the  number  of 
ohms  in  a  given  uniform  conductor,  such  as 
a  copper  wire,  depends  upon  the  length  of 


!  "UNIVERSITY 


36  ELECTRIC    STREET   RAILWAYS. 

the  wire,  upon  its  area  of  cross-section  and 
upon  its  physical  condition.  The  longer 
and  narrower  a  wire,  the  greater  will  be 
its  electric  resistance.  In  the  same  way, 
the  longer  and  narrower  a  pipe,  the 
greater  its  water  resistance;  on  the  con- 
trary, the  shorter  a  wire  and  the  greater  its 
area  of  cross-section,  the  smaller  will  be 
its  resistance.  An  ordinary  copper  trolley 
wire,  which  is  No.  0,  American  Wire 
Gauge,  with  a  diameter  of  0.325",  has  a 
resistance  per  mile  of,  approximately,  half 
an  ohm,  so  that  2  miles  of  this  wire 
would  have  a  resistance  of,  approximately, 
1  ohm,  and  1  foot  of  the  wire  would 

have   a    resistance   of   J      x       = 


ohm,  approximately.  If  the  trolley  wire 
instead  of  being  No.  0  gauge  were  No. 
0000,  which  is  a  wire  about  twice  as  heavy 
as  No.  0,  having  a  diameter  of  0.46",  it 


ELEMENTARY    ELECTRIC   PRINCIPLES.       37 

would  have  only  half  the  resistance  of  No. 
0,  and,  therefore,  approximately,  l/4th  ohm 
per  mile. 

In  Fig.  5,  five  copper  wires,  having  dif- 
ferent   lengths    and     areas    of    cross-sec- 


B  10 
A  10 
O  10 


FIG.  5. — RESISTANCE  OF  WIRES. 

tion,  are  diagrammatically  represented. 
A,  represents  a  trolley  wire  1  mile  long 
and  0.325"  in  diameter,  having,  there- 
fore, a  resistance  of  approximately  0.5 
ohm.  13,  is  a  wire  2  miles  long  of  the 


38  ELECTRIC    STREET    RAILWAYS. 

same  cross-section,  and,  therefore,  offer- 
ing 1.0  ohm.  C)  is  a  wire  half  a  mile 
long  of  the  same  cross-section,  and, 
therefore,  offering  a  resistance  of,  approxi 
mately,  0.25  ohm.  _/>,  is  a  wire  1  mile 
long,  but  having  a  cross-section,  as  repre- 
sented on  the  left  hand  side,  say  twice  that 
of  any  of  the  wires,  A,  B,  or  C.  It  will, 
therefore,  have  half  the  resistance  of  A,  or 

05  * 

-—  =  0.25   ohm.     E,  is  a   wire  0.65"  in 
2i 

diameter,  having,  therefore,  four  times  the 
cross-section  of  A,  and  being  2  miles  in 
length.  If  the  wire  were  of  the  same  cross- 
section  as  A,  it  would  have  0.5  x  2  =  1 
ohm,  but  being  four  times  as  heavy,  its 
resistance  will  be  one-quarter  of  this,  or 

-^-  =  0.25    ohm.      Consequently,     C,    D, 

and  E^  have  all  the  same  resistance, 
although  their  dimensions  are  so  different. 


ELEMENTARY    ELECTRIC    PRINCIPLES.       39 

If,  therefore,  the  cross-section  and 
length  of  any  copper  wire  be  known,  we 
can  determine  what  its  resistance  will  be, 
assuming  that  the  conducting  power  of  the 
substance  of  the  wire  is  the  same  as  that 
of  the  trolley  wire  we  have  selected  as  our 
standard.  The  resistance  will  be  directly 
proportional  to  the  length,  and  inversely 
proportional  to  the  area  of  cross-section ; 
or,  in  other  words,  if  the  length  be  doubled 
the  resistance  will  be  doubled,  while  if 
the  area  of  cross-section  be  doubled  the 
resistance  will  be  halved. 

We  have  hitherto  considered  copper 
wires  only  in  estimating  the  resistance  oi 
a  circuit.  When  any  other  conducting 
material,  such  as  iron,  is  employed,  the 
resistance  of  a  wire  having  a  given  length 
and  cross-section  will  be  materially  dif- 
ferent. Thus,  an  iron  wire  has,  approxi- 


40  ELECTRIC    STREET    RAILWAYS. 

mately,  6  1/2  times  as  mucli  resistance  as 
a  wire  of  copper  of  equal  dimensions. 
Iron  trolley  wires  are,  therefore,  never 
used,  for  the  reason  that  it  would  be  nec- 
essary to  employ  a  wire  having  about  6  1/2 
times  the  cross-section  of  ordinary  trolley 
wire  to  have  the  same  conductance ;  i.  e., 
ability  to  conduct  electric  current.  Iron, 
however,  enters  into  street  railway  circuits 
in  the  form  of  the  tracks,  which,  as  we 
have  seen,  form  a  portion  of  the  return 
circuit  to  the  power  house. 

The  dimensions  of  a  wire  which  has  a 
resistance  of  1  ohm  will  necessarily  vary 
with  the  character  of  the  material  of  which 
the  wire  is  composed.  Thus,  in  copper,  its 
length  might  be  approximately  2  miles,  if 
its  diameter  was  that  of  a  trolley  wire, 
0.325";  or,  its  length  might  be  only  1 
foot,  if  of  No.  40  American  Wire  Gauge, 


ELEMENTARY   ELECTRIC    PRINCIPLES.      41 

having  a  diameter  of  0.003145" ;  if  of  iron, 
a  length  of  about  900  feet  of  trolley  wire ; 
and,  roughly,  2  inches  of  No.  40  wire 
would  have  a  resistance  of  1  ohm.  In 
all  cases  the  exact  resistance  would  de- 
pend upon  the  degree  of  purity  of  the 
metal,  as  well  as  upon  its  physical  condi- 
tion ;  that  is  to  say,  upon  its  hardness, 
and  temperature.  Since  mercury  is  a 
metal,  which  is  fluid  at  ordinary  tem- 
peratures, and  can  be  readily  obtained  in  a 
nearly  homogeneous  and  pure  condition, 
the  ohm  has  been  practically  defined  as 
the  resistance  of  a  column  of  mercury 
1.063  metres  in  length,  and  1  square 
millimetre  in  cross-section,  at  the  temper- 
ature of  melting  ice. 

It  is  evident  from  what  we  have  said 
that  the  quantity  of  water  which  flows,  in 
any  given  time,  through  the  pipe  referred 


42  ELECTKIC    STREET   RAILWAYS. 

to  in  connection  with  Fig.  3,  will  depend 
both  on  the  pressure  or  head  of  water  in 
the  reservoir,  as  well  as  upon  the -resist- 
ance which  the  pipe  offers  to  the  now.  In 
the  case  of  the  electric  circuit  the  same 
rule  applies,  that  is  to  say,  the  quantity  of 
electricity  which  passes  or  flows  in  an  elec- 
tric circuit,  depends  not  only  upon  the 
electric  pressure  in  the  circuit  which 
causes  the  flow,  but  also  upon  the  resis- 
tance of  the  circuit  which  opposes  it. 

In  the  case  of  the  electric  circuit  the 
electric  current  is  related  to  the  E.  M.  F. 
and  to  the  resistance  in  accordance  with  a 
law  generally  known  as  Ohm's  law.  This 
law  may  be  expressed  as  follows : 

The  current  strength  in  amperes  flowing 
through  a  circuit,  varies  directly  with  the 
pressure  or  E.  M.  F.,  and  inversely  with 


ELEMENTARY    ELECTRIC   PRINCIPLES.      43 

the  resistance ;  so  that  if  we  divide  the 
number  of  volts  in  the  E.  M.  F.  by  the 
number  of  ohms  in  the  resistance,  we  obtain 
the  current  strength  in  amperes;  or,  con- 
volts 

cisely,  amperes  =    -r . 

ohms 

Thus,  if  a  circuit  contains  an  E.  M.  F.  of 
10  volts,  and  a  resistance  of  5  ohms,  the 

current  in  the  circuit  would  be  -~-  —    2 
amperes. 

We  have  seen,  in  connection  with  Fig.  3, 
that  the  quantity  of  water  which  flows  per 
second  through  the  water  pipe  from  the 
reservoir,  depends  both  on  the  pressure  at 
the  reservoir,  and  on  the  resistance  of  the 
pipe.  This,  however,  is  only  true  when  no 
obstacle  to  the  flow  of  the  water  exists  save 
the  resistance  of  the  pipe  itself.  If,  for 
example,  instead  of  permitting  the  water 


44 


ELECTRIC   STREET   RAILWAYS. 


to  escape  freely  from  the  open  end  of  the 
pipe  it  be  first  caused  to  pass  through,  and 
actuate,  a  water  motor,  then  the  condi- 
tions of  flow  will  be  profoundly  modified, 
much  less  water  flowing  through  the  pipe 
in  the  second  case  than  in  the  first.  If,  for 


FIG.  6. — HYDRAULIC  GRADIENT. 

example,  as  in  Fig.  6,  the  reservoir  H,  is 
capable  of  discharging  by  the  pipe  A  k', 
either  through  the  faucet  &',  into  the  air, 
or  through  the  faucet  ?,  after  passing 
through  the  motor  M,  the  flow  in  the  two 
cases  will  be  very  different.  In  the  first 

ft/tU/L££  ~ 

case  thej)ressure  at  the  reservoir  will  be 
that  due  to  the  height  of  the  water  A  A', 
say  50  feet,  while  the  pressure  at  the  dis- 


ELEMENTARY    ELECTRIC    PRINCIPLES.      45 

charge  point,  will  simply  be  that  of  the 
external  air,  or  a  column  of  0  feet.  In 
other  words  in  discharging  through  the 
pipe  the  water  pressure  suffers  a  drop  as 
represented  by  the  dotted  line  A  k',  and 
the  pressure  at  the  intermediate  points  is 
indicated  by  the  points  V,  c ,  d',  e',  f,  g',  li. 
If,  however,  the  faucet  &',  be  closed,  and 
that  at  I,  be  opened,  thereby  establishing 
communication  through  the  water  motor 
M,  the  motor  will  commence  to  operate, 
and  in  so  doing  will  develop  a  back  pres- 
sure, or  counter  watermotive  force,  which 
opposes  the  flow  of  water  and  acts  like  a 
resistance.  The  pressure  at  Jc',  under  these 
circumstances,  instead  of  being  0  feet,  wrill 
rise  to  &2,  and  the  drop  of  pressure,  which 
has  taken  place  in  the  tube  A  ~k ',  will  have 
diminished  from  A  A'  to  If  L,  with  a  cor- 
respondingly reduced  flow  of  water  through 
the  pipe. 

/^  ^         OF  THE 

TJNIVERSITTT, 


46 


ELECTKIC    STREET   RAILWAYS. 


Similarly,  if  the  electric  circuit  repre- 
sented in  Fig.  2,  be  so  modified  as  in  Fig. 
7,  that  it  may  be  closed  either  at  c  c,  di- 
rectly back  through  the  track,  or  at  If, 


FIG.  7. — ELECTRIC  GRADIENT. 

through  an  electric  motor  J/J  the  electric 
flow  or  current  in  amperes  will  be  very 
different  in  the  two  cases.  If  the  circuit 
be  closed  through  the  track  wire  at  c  c, 
the  pressure,  at  A,  will  be  say  500  volts, 
as  represented  by  the  dotted  line  A  a,  and 
supposing  the  length  A  H,  to  be  1  mile 
of  trolley  wire,  then  neglecting,  for  con- 


ELEMENTARY    ELECTRIC   PRINCIPLES.      47 

venience,  the  resistance  of  the  track  and 
generator,  the  resistance  of  the  circuit  will 
be  0.5  ohm,  and  the  current  strength  in 
the  circuit  500  volts  +  0.5  ohm  =  1,000 
amperes. 

If,  however,  the  circuit  be  closed  through 
the  motor  M,  the  latter  will  be  actuated  by 
the  current  and  will  be  set  into  rotation, 
whereby  a  back  pressure,  or  Counter  electro- 
motive force,  usually  abbreviated  C.  E. 
M.  F.,  will  be  set  up  in  the  motor, 
of  say,  450  volts,  as  represented  by  the 
dotted  line  H  li  ;  so  that  the  effective 
pressure  or  E.  M.  F.  which  drives  the 
current  through  the  circuit,  will  be  re- 
duced to  hh'  -  500  —  450  =  50  volts, 
and  the  current  strength,  neglecting  the 
resistance  of  the  generator  motor  and 
track,  will  be,  50  volts  -=-  0.5  ohm  =  100 
amperes. 


48  ELECTRIC   STKKET   RAILWAYS. 

A  flow  of  water  is  sometimes  rated  as 
being  a  certain  quantity  of  water ;  i.  e.,  a 
certain  number  of  cubic  feet  or  gallons  per 
second.  In  the  same  way  the  electric  flow 
may  be  rated  as  being  a  certain  quantity 
of  electricity  passing  through  the  circuit 
per  second.  The  unit  of  electric  quantity 
is  called  the  coulomb,  and  has  been  so 
chosen  that  a  flow  of  1  coulomb  per  sec- 
ond is  called  an  ampere.  Consequently,  a 
flow  or  current  of  1  ampere,  maintained  in 
a  circuit  for  1  minute,  represents  a  total 
flow  of  60  coulombs  of  electricity,  and, 
maintained  for  one  hour,  a  total  flow  of 
3,600  coulombs. 

When  an  E.  M.  F.  acts  on  a  broken  or 
open  circuit,  it  is  unable  to  send  any 
current  through  the  circuit,  and  will, 
therefore,  do  no  work.  Thus,  when  the 
generator  at  the  power  house  is  driven 


ELEMENTARY    ELECTRIC    PRINCIPLES.      49 

by  an  engine  and  supplies  an  E.  M.  F. 
of  500  volts  to  the  trolley  system  con- 
nected with  it,  no  current  will  pass 
through  the  generator  if  there  be  no  cars 
on  the  line,  assuming  that  the  wires  are 
properly  insulated.  Under  these  circum- 
stances the  generator  will  not  be  supply- 
ing any  power,  and  the  engine  will  have 
no  work  to  do  except  to  drive  the  genera- 
tor against  its  friction.  In  fact,  except 
that  the  generator  armature  is  magnetized, 
it  behaves  like  a  mere  wheel  of  copper 
and  iron,  so  supported  on  an  axis  in  bear- 
ings, that  it  might  be  rotated  with  a  very 
small  expenditure  of  power.  When,  how- 
ever, the  circuit  of  the  generator  is  closed 
by  the  connection  of  the  cars  with  the 
trolley  wire,  so  that  a  current  is  trans- 
mitted through  the  circuit  or  circuits 
under  the  pressure  of  500  volts,  the 
generator  does  work  at  a  rate  which  will 


50  ELECTRIC    STREET   RAILWAYS. 

depend  upon  the  amount  of  current  sup- 
plied, the  greater  the  current  strength  in 
amperes  delivered  to  the  trolley  system, 
and  distributed  to  the  cars,  the  greater 
will  be  the  activity  which  the  generator 
has  to  supply,  and  the  greater  will  be  the 
activity  which  the  engine  must  supply  to 
drive  it,  so  that  when  the  load  conies  on 
the  system  by  the  operation  of  the  cars, 
the  generator  which  previously  required 
say  20  horse-power  only  to  revolve  it, 
may  now  require  the  engine  to  supply  500 
horse-power,  which  activity  will  be  trans- 
formed into  electric  activity  in  the  circuit. 
If  we  multiply  the  pressure  in  volts  by 
the  current  strength  in  amperes  which  is 
being  supplied  by  that  pressure,  we  obtain 
the  activity  supplied  in  watts.  Thus,  if 
a  generator  supplying  550  volts  at  its 
terminals  to  a  trolley  system  delivers  a 
current  strength  of  50  amperes  through 


ELEMENTARY    ELECTRIC   PRINCIPLES.      51 

the  circuit  containing  its  armature,  trolley, 
street-car  motor,  and  track,  then  the  ac- 
tivity supplied  by  the  generator  at  its  ter- 
minals will  be  550  volts  X  50  amperes  = 
27,500  watts  =  27.5  kilowatts  (usually  ab- 
breviated KW)  =  36.85  HP  =  27,500 
joules-per-second  =  20,268  foot-pound  s-per- 
second.  The  engine  would  have  to  supply 
more  power  than  this  to  the  genera- 
tor, since  it  would  have  to  make  up 
for  the  loss  of  power  in  the  generator 
owing  to  its  mechanical  and  electrical  fric- 
tions, but  if  the  generator  had  an  efficiency 
of  90  per  cent.,  that  is  to  say,  if  its  output 
was  90  per  cent,  of  its  intake,  then  the 
activity  which  the  engine  would  have 
to  supply  to  the  generator  would  be 

=  30>555  watts  =  3(X555 


KW   =   40.94   HP         30,555   joules-per- 
second  =  22,517  foot-pounds-per-second. 


52  ELECTRIC    STREET   RAILWAYS. 

Just  as  the  total  amount  of  work  ex- 
pended by  water  escaping  from  a  reser- 
voir, is  equal,  in  foot-pounds,  to  the 
number  of  pounds  of  water  multiplied  by 
the  number  of  feet  through  which  it  falls, 
so  the  total  amount  of  work  expended  by 
electricity  in  flowing  through  a  conductor 
or  circuit  is  equal,  in  joules,  to  the  number 
of  coulombs  of  electricity  multiplied  by 
the  number  of  volts  difference  of  electric 
level,  or  pressure,  under  which  it  passes. 
Thus  a  current  of  50  amperes  flowing 
under  a  pressure  of  550  volts,  represents  a 
flow  of  50  coulombs-per-second  under  that 
pressure  and  an  amount  of  work  equal  to 
50  x  550  =  27,500  joules  in  each  second, 
or,  in  one  hour  of  3,600  seconds,  a  total 
work  of  3,600  X  27,500  =  99,000,000 
joules.  But  Ave  have  seen  that  the  ac- 
tivity in  this  circuit  is  27,500  watts,  and 
this  activity  maintained  for  an  hour  will 


ELEMENTARY   ELECTRIC    PRINCIPLES.      53 

require  an  expenditure  of  27,500  watt- 
hours,  or  27.5  kilowatt-hours.  A  watt- 
liour  is,  therefore,  a  quantity  of  work  equal 
to  3,600  joules,  or  2,657  foot-pounds,  while 
a  Jdlowatt-kowr,  the  unit  of  work  usually 
employed  with  large  electric  machines,  will 
be  1,000  times  as  much,  or  3,600,000 
joules  =  2,657,000  foot-pounds. 

If  a  pressure  of  550  volts  is  maintained 
steadily  at  the  generator  terminals,  under 
all  conditions  of  load,  the  pressure  at  the 
trolley  of  the  single  car  we  have  con- 
sidered, will  be  less  than  500  volts  by  an 
amount  which  will  depend  upon  the  size 
and  number  of  the  conductors  in  the  net- 
work supplying  it,  and  upon  the  length  of 
those  conductors,  or  the  distance  of  the 
car  from  the  power  house.  Thus,  if  the 
car  be  1  mile  from  the  power  house,  and 
if  the  track  have,  for  simplicity,  a  negligi- 


54  ELECTRIC    STREET   RAILWAYS. 

ble  resistance,  while  the  single  trolley  wire 
supplying  the  car  has  a  resistance  of  0.5 
ohm  per  mile,  then  the  resistance  between 
the  generator  and  the  car  will  be  0.5 
ohm,  and  the  drop  in  this  length  of  con- 
ductor will  be  50  amperes  X  0.5  ohm  = 
25  volts,  so  that  the  pressure  at  the  termi- 
nals of  the  car  motor  as  determined  by 
a  voltmeter,  or  instrument  for  measuring 
the  number  of  volts,  would  be  550  —  25  = 
525  volts,  and  when  the  car  was  operating, 
the  voltmeter,  if  connected  between  the 
trolley  wire  and  the  track  at  the  car, 
would  show  this  pressure,  while  as  soon  as 
the  car  was  disconnected  by  opening  the 
switch,  the  pressure  between  the  trolley 
wire  and  the  track  would  immediately 
rise  to  550  volts,  assuming  no  other  car  or 
leakage  current  to  exist  over  the  system. 
The  amount  of  drop  which  will  be  pro- 
duced over  a  given  length  of  conductor 


ELEMENTARY   ELECTRIC   PRINCIPLES.      55 

will  depend  entirely  upon  the  current 
strength,  so  that  if  we  double  the  current 
strength  we  double  the  drop. 

The  activity  which  the  motor  will 
receive  at  its  terminals  will  be  the  current 
strength  in  amperes,  (which  is  the  same 
all  through  the  circuit  when  only  one  car 
is  employed,)  multiplied  by  the  pressure  at 
its  terminals.  Thus,  in  the  preceding  case, 
the  pressure  being  525  volts  at  the  motor 
terminals  between  trolley  and  track,  while 
the  current  strength  is  50  amperes,  the 
activity  absorbed  by  the  motor  will  be 
525  volts  X  50  amperes  =  26.25  KW,  or 
1.25  KW  less  than  that  supplied  by  the 
generator  to  the  line.  This  activity  of 
1.25  KW  is  expended  in  the  line  as  heat, 
uniformly  distributed  through  its  sub- 
stance ;  for,  the  drop  being  25  volts,  and 
the  current  strength  50  amperes,  the  activ- 


56  ELECTRIC    STREET    RAILWAYS. 

ity  expended  in  this  conductor  will  be  25 
volts  X  50  amperes  —  1,250  watts,  ==  1.25 
KW  expended  entirely  as  heat. 

Of  the  26.25  KW  delivered  to  the 
motor,  only  a  certain  fraction  will  be  use- 
fully employed  in  driving  the  car,  the 
remainder  being  uselessly  expended  in 
heating  the  motor.  If  the  efficiency  of 
the  motor  be  80  per  cent.,  then  the  activity 
usefully  expended  in  the  preceding  case 

QA 

will  be  26.25   X  =  21  KW    =  28.14 


HP  =  21,000  joules-per-second  15,480 
foot-pounds-per-second.  This  activity  will 
be  supplied  to  the  shaft  of  the  motor. 
Assuming  at  present  that  no  power  is 
wasted  in  gears,  then  this  activity  will  be 
available  for  propelling  the  car.  For 
example,  if  the  car  friction  were  very 
small,  and  its  total  weight,  including 


ELEMENTAEY   ELECTRIC    PRINCIPLES.      57 

passengers  was  30,000  pounds,  then  the 
activity  supplied  would  be  capable  of  lift- 
ing 30,000  pounds  through  a  distance  of 

15.480 

t»Q  ..Q,.   =  0.516  toot-per-second.      With  a 

1  per  cent,  grade  this  would  represent  a 
speed  of  51.6  feet-per-second,  or  35.2  miles- 
per-hour,  and  with  a  10  per  cent,  grade 
it  would  represent  a  speed  of  5.16  feet 
per  second,  or  3.52  miles-per-hour. 

It  is  evident,  therefore,  that  the  activity 
which  can  be  communicated  to  a  moving 
car  for  a  given  activity  supplied  at  the 
driving  shaft  of  the  engines,  depends  upon 
the  efficiency  of  the  generator,  the  effi- 
ciency of  the  motor,  and  the  efficiency  of 
the  line  conductor,  including  under  this 
term,  the  track. 

The  efficiency  of  a  motor  or  generator  is 


58  ELECTRIC    STREET   EAILWAYS. 

the  ratio  of  the  output  to  the  intake.  The 
efficiency  of  a  line  conductor  or  circuit 
may  also  be  regarded  as  the  ratio  of  the 
output  to  the  intake,  the  intake  being 
measured  at  the  generator  terminals  and 
the  output  at  the  motor  terminals.  The 
efficiency  of  a  generator  or  a  motor  usually 
increases  with  the  load  up  to  full  load  or 
nearly  full  load,  so  that,  under  ordinary 
circumstances  the  more  work  we  can  get 
the  motor  or  generator  to  do,  within  the 
limits  of  its  capacity,  the  greater  the  propor- 
tion of  useful  work  delivered,  to  the  work 
received,  although  the  loss  of  work  will 
be  absolutely  greater.  Thus,  a  street  car 
motor,  whose  maximum  activity  is  rated 
at  15  KW  (approximately  20  HP)  would 
require,  perhaps,  2  KW  to  run  it  when 
entirely  free  from  all  load  or  disconnected 
from  its  gears ;  i.  e.,  when  doing  no  use- 
ful work,  so  that  its  efficiency  would  be 


ELEMENTARY   ELECTRIC    PRINCIPLES.       59 

—  =  o.     When    fully  loaded,  however,  it 

might  waste  3  KW  and  deliver  15  KW, 
so  that  its  intake  would  be  18  KW,  and 

15 
its  efficiency  y^-  =0.833  =  8 3. 3  per   cent. 

Its  efficiency  may,  therefore,  increase  from 
0  to  83.3  per  cent,  from  no  load  to  full 
load,  although  the  actual  loss  of  activity 
in  it  would  increase  in  the  same  range 
from  2  KW  to  3  KW.  The  same  princi- 
ples apply  to  a  generator,  and  for  this 
reason  it  is  always  more  economical  to 
operate  generators  at  a  fair  proportion  of 
their  full  load. 

In  the  case  of  the  line  conductor  or  con- 
ductors, including .  track  conductors,  the 
case  is  different.  The  efficiency  is  always 
less  as  the  load  increases.  Thus,  if  we 
supply  a  current  strength  of  1  ampere 
over  a  circuit  of  trollev  conductor  and 


60  ELECTRIC    STREET   RAILWAYS. 

track,  having  a  total  resistance  of  1  ohm, 
then  the  drop  in  this  circuit  will  be 
1  ampere  X  1  ohm  —  1  volt,  and  if  the 
pressure  at  the  motor  be  kept  at  500  volts, 
the  pressure  at  the  generator  will  have  to 
be  adjusted  to  501  volts  ;  or,  if  the  pressure 
at  the  generator  be  kept  at  500  volts,  the 
pressure  at  the  motor  terminals  will,  with 
a  current  of  1  ampere,  automatically  be- 
come 499  volts.  If,  however,  2  amperes 
be  supplied  through  the  same  circuit, 
the  drop  will  double,  or  will  become  2 
volts,  and  the  pressure  at  the  generator 
will  be  502  volts,  if  that  at  the  motor  is 
500.  In  the  former  case  the  efficiency  of 

the  line  circuit  will  be       r  ;  in  the  latter 


case  it  will  be  -  .     Similarly,  if  the  cur- 

rent strength  be  increased  to  100  amperes, 
the  drop   will  increase   to  100  volts,  and 


ELEMENTARY   ELECTRIC   PRINCIPLES.      61 

with  500  volts  at  the  generator  there  will 
be  400  volts  left  at  the  motor,  making  the 

400 
efficiency  ™r  =  0.8  ==  80  per  cent.     It  is 

evident,  therefore,  that  the  efficiency  of  the 
line  continuously  decreases  with  the  load. 

It  is  clear  from  the  preceding  that  if 
a  trolley  wire  were  very  long,  say  15 
miles,  so  that  its  resistance  was  7.5  ohms, 
then  the  current  strength  of  50  amperes 
passing  through  the  circuit  to  operate  the 
car  motor  at  the  extreme  distance  from 
the  power  house  would  produce  a  drop  of 
50  amperes  x  7.5  ohms  =  375  volts,  leaving 
only  175  volts  pressure  at  the  motor  when 
550  volts  was  the  pressure  at  the  generator 
terminals,  and  assuming  no  resistance  in 
the  ground-return  circuit.  The  activity 
delivered  by  the  generator  would  be  550 
volts  x  50  amperes  =  37.5  KW.  The 


62  ELECTRIC    STREET   RAILWAYS. 

activity  available  at  the  motor  terminals 
would  only  be  175  volts  X  50  amperes  = 
8.75  KW,  so  that  the  efficiency  of  the  line 

O    ^7  K 

would   only    be   ^  =  0.319  =  31.9    per 

cent.,  while  the  available  speed  of  the  car 
would  be  correspondingly  reduced.  In 
other  words,  owing  to  the  great  length  of 
conductor,  and  resistance  in  the  circuit,  a 
large  percentage  of  the  activity  would  be 
expended  in  heating  a  long  length  of  wire, 
instead  of  driving  the  car. 

The  same  condition  of  line  efficiency 
would  be  produced  by  a  number  of  cars 
over  a  shorter  length  of  circuit.  Thus, 

o 

reverting  to  the  case  of  a  single  mile  of 
trolley  wire,  if  a  bunch  of  five  trolley  cars 
should  start  together  from  the  distant  end 
of  the  line  towards  the  power  house,  each 
taking  50  amperes  of  current  strength,  the 


ELEMENTARY   ELECTRIC    PRINCIPLES.      63 

total  current  strength  supplied  to  the 
bunch  would  be  250  amperes,  and  the 
drop  in  the  line  would  be  250  amperes 
X  0.5  ohm  =  125  volts,  making  the  pres- 
sure at  the  bunch  425  volts.  The  line 
efficiency,  under  these  conditions  would 

425 

be  ^-r  —  0.772  =  77.2  per  cent.     Conse- 
o50 

sequently,  when  the  distance  to  whicli  cars 
have  to  be  run  is  great,  or,  when  the 
number  of  cars  and  the  current  strength 
to  be  collectively  supplied  are  great,  the 
amount  of  copper  employed  to  supply  the 
system  must  be  increased  so  as  to  reduce 
the  effective  conductor  resistance.  If,  for 
example,  we  double  the  area  of  cross-sec- 
tion of  the  trolley  wire,  and,  therefore,  its 
weight  per  mile,  we  halve  the  resistance  of 
the  conductor  per  mile  and,  consequently, 
halve  the  drop,  excluding  track  resistance, 
and,  therefore  halve  the  drop  which  will 


64  ELECTRIC    STREET   RAILWAYS. 

occur  at  any  given  distance  with  any  given 
load. 


There  is,  however,  an  obvious  limit  to 
the  size  of  trolley  wire  which  can  he  prac- 
tically employed.  In  fact,  trolley  wires 
are  almost  always  constructed  of  No.  0, 
A.  W.  G.  They  are  supplemented,  how- 
ever, in  practice,  by  what  are  called 
feeders;  i.  e.,  feeding  conductors  which 
are  separate  from  the  trolley  wires,  but 
which  lead  from  the  generator  in  the 
power  house  and  connect  with  the  trolley 
wire  at  suitable  distances  along  the  track. 
Thus  in  Fig.  8,  Gr,  is  the  generator,  and 
C,  a  car  at  a  certain  distance  along  the 
track.  &  f\,  a  Ft,  G  F*  G  F*  four 
separate  feeders  connecting  with  the  trolley 
wire  at  different  distances.  As  shown  in 
the  diagram,  the  current  strength  required 
to  supply  the  car,  is  probably  supplied 


ELEMENTARY    ELECTRIC   PRINCIPLES.       65 

in  a  large  measure  by  feeder  G  F^  so  that 
the  feeders  G  F2,  G  ^  and  G  F4j  are 
comparatively  idle.  Consequently,  the  drop 
of  the  feeder  G  F^  will  be  comparatively 


FIG.  8.  —  FEEDER  SYSTEM. 


great  with  reference  to  that  of  the  other 
feeders.  F^  F%,  F&  and  F^  are  called  feed- 
ing points. 

In  practice  it  is  usual  to  so  arrange  the 
feeders  and  the  distances  between  feeding 
points,  that  when  all  the  cars  are  being 


66  ELECTRIC    STREET   RAILWAYS. 

operated  at  average  distances,  the  drop 
shall  nowhere  be  in  excess  of  50  volts,  and, 
therefore,  that  with  550  volts  at  the  gene- 
rator terminals  the  pressure  shall  not  be 
lower  than  500  volts  at  any  point  on  the 
line. 


OF  THE 

-TIVERSITT 


CHAPTER  IV. 

THE    MOTOR. 

As  is  well  known,  the  power  which  pro- 
pels a  trolley  car  is  obtained  from  the 
electric  current  transmitted  through  the 
circuit,  by  the  intervention  of  an  electric 
motor  or  motors,  there  being  usually  two 
motors  placed  on  the  truck  of  an  ordinary 
street  car.  Fig.  9,  shows  the  general  con- 
struction of  a  truck  with  two  motors  J/J 
M,  in  place,  one  geared  to  the  axle  of  each 
pair  of  wheels.  Reserving  for  description 
in  Chapter  V.  the  different  methods 
adopted  for  the  mounting  or  hanging  of 
a  motor,  as  well  as  the  details  in  the 
construction  of  the  car  truck,  we  will  now 


00  ELECTRIC    STREET    RAILWAYS. 

proceed  to  the  general  description  of  the 
motor,  its  construction  and  operation. 

Fig.  10  shows  a  form  of  electric  motor 
in  extended  use.     Here  the  motor  is  coin- 


FIG.  9. — CAR  TRUCK  WITH  MOTORS  IN  PLACE. 

pletely  enclosed  in  a  cast-steel  frame  F,  F, 
F,  made  in  two  halves,  fitted  together,  as 
shown.  Since  the  motor  runs  within  a  few 
inches  of  the  surface  of  the  street,  and  is, 
therefore,  exposed  to  dust,  mud  and  water, 
it  becomes  absolutely  necessary  not  only  to 
^provide  it  with  a  casing,  but  also  to  make 
this  casing  practically  air  and  water  tight. 
The  main  shaft  of  the  motor  is  seen  pro- 


THE   MOTOR. 


69 


jecting  through  its  bearing  at  Ay  and  this 
bearing   is  lubricated  by  the  grease  box  O. 


FIG.  10.— FORM  OF  ELECTRIC  MOTOR. 

The  armature  shaft  is  connected  with  the 
axle  of  the  wheels  on  which  the  truck 
rests,  by  gear  ivheels  enclosed  in  the  gear 
cover  6r,  G.  The  gears  are  inserted  in 


70  ELECTRIC    STREET    RAILWAYS. 

order  to  reduce  the  speed  of  the  car  as 
well  as  to  increase  the  effective  pull  of 
the  motor,  as  will  be  more  clearly  pointed 
out  subsequently.  The  main  axle  passes 
through  the  bearing  B,  lubricated  by  the 
grease  box  C'.  The  motor  is  supported 
on  the  truck  by  the  lugs  Z',  L'.  Access 
to  the  working  parts  of  the  motor  is  had 
by  the  lid  L,  L,  L,  while  a  more  nearly 
complete  inspection  can  be  obtained  by 
unscrewing  two  bolts,  one  of  which  is  seen 
at  B,  and  throwing  back  the  upper  half  of 
the  motor  upon  hinges  H,  H.  The  insu- 
lated cables  K,  K,  pass  through  holes  in 
the  castings  and  supply  electric  current  to 
the  motor.  This  particular  motor  is  called 
a  Gr.  E.  800  motor,  the  number  800  repre- 
senting that  it  is  capable  of  exerting  on 
the  car  a  push  of  800  Ibs.  weight  at  the 
main  axle,  when  supplied  with  the  full  cur- 
rent strength,  and  mounted  on  33"  wheels 


THE   MOTOR.  71 

on  level  rails.  Two  such  motors  when  sup- 
plied with  full  current  strength,  therefore, 
give  a  push  of  1,600  Ibs.  weight  to  a  car. 

Fig.  11,  shows  the  same  motor  with  the 
upper  half  thrown  back  on  its  hinges,  thus 
permitting  an  inspection  of  the  parts  of 
the  motor.  Here,  as  in  all  this  class  of 
electric  motors,  the  essential  parts  consist 
of  an  armature  or  rotating  part  A  A,  with 
a  commutator  at  M  M,  upon  which  rest 
the  brushes  (7,  (7,  which  carry  the  current 
from  the  trolley  line  into  and  out  of  the 
armature.  The  armature  rotates  between 
four  poles,  of  which  one  is  shown  in  the 
upper  lid  at  P,  surrounded  by  a  magnetiz- 
ing coil  of  wire  W.  The  armature  shaft 
has  a  pinion  N,  secured  to  one  of  its  ex- 
tremities, which  engages  with  a  gear-wheel 
on  the  main  axle  of  the  truck,  which  axle 
passes  through  the  bearings  JB,  B. 


72  ELECTRIC    STREET   RAILWAYS. 

The  armature  of  one  of  the  electric 
motors  above  described  consists  essentially 
of  three  parts ;  namely,  the  armature 


FIG.  11.— MOTOR  OF  FIG.  10  OPENED. 

core,  mounted  on  its  shaft,  the  armature 
windings  or  coils,  which  are  placed  on 
the  armature,  and  the  commutator.  The 


THE   MOTOR. 


73 


general  appearance  presented  by  an  arma- 
ture core,  mounted  on  its  shaft,  is  shown 
in  Fig.  12.  Here,  as  will  be  seen  from  an 


FIG.  12. — UNWOUND  ARMATURE. 


inspection  of  the  figure,  the  core  consists 
of  a  cylindrical  body  made  of  soft  iron, 
If  the  armature  core  be  made  from  a 


74  ELECTRIC    STREET   RAILWAYS. 

solid  mass  of  iron,  it  has  been  found  by  ex- 
perience that  during  the  changes  in  mag- 
netization to  which  it  is  subjected,  when  it 
rotates,  deleterious  electric  currents  called 
eddy  currents,  are  generated  in  it.  These 
currents  cannot  be  employed  in  the  ex- 
ternal circuit. ;  they  merely  serve  to  heat 
the  armature  core  and  so  prevent  the  effi- 
cient operation  of  the  motor.  By  adopt- 
ing the  simple  expedient  of  laminating  the 
core ;  that  is,  of  forming  it  of  thin  sheets 
of  iron,  laid  side  by  side,  this  difficulty  is 
avoided.  The  armature  core  shown  in 
Fig.  12,  is  laminated,  that  is,  formed  of 
discs  or  rings  clamped  together  and  sup- 
ported at  right  angles  to  the  axis  of  the 
shaft.  The  edges  of  the  cylindrical  iron 
core  thus  formed  are  provided,  circuni- 
ferentially,  with  a  series  of  longitudinal 
grooves  or  recesses,  as  shown.  These  are 
intended  for  the  reception  of  the  insulated 


THE   MOTOR.  75 

copper  conductors  that  carry  the  electric 
current. 

In  placing  the  insulated  copper  wire  on 
the  armature  core,  care  is  necessary  to  ob- 
tain a  symmetrical  disposition  of  the  wires. 
One  method  of  arranging  the  conductors 
on  the  core  is  shown  in  Fig.  13,  which 
represents  an  armature  in  the  process  of 
winding.  Armatures  for  motors  are  made 
in  a  variety  of  forms  of  which,  perhaps, 
the  ring  armature  and  the  cylinder  arma- 
ture are  the  commonest.  The  armature 
shown  in  Fig.  13  is  of  the  cylinder  type. 
Here  the  wire  is  wound  only  on  the  out- 
side of  the  core.  A  single  cotton-covered 
wire,  starting  at  say  A,  passes  to  J3,  through 
the  grooves,  provided  on  the  surface  of 
the  core  for  its  reception.  It  then  de- 
scends to  O,  in  the  curved  path  shown, 
turns  inwards  and  passes  on  to  D,  when  it 


76 


ELECTRIC    STREET   RAILWAYS. 


again  crosses  through  the  groove  to  JSJ  and 
so  on.  All  the  wires  which  are  left  pro- 
jecting on  the  left-hand  side  are  intended 


FIG.  13. — ARMATURE  IN  PROCESS  OF  WINDING. 

to  be  connected  to  the  part  called  the  com- 
mutator, the  object  of  which  will  be  ex- 
plained subsequently. 

A  particular    form    of    commutator    is 
shown   in  Fig.  14.     It  consists,  as  shown, 


THE   MOTOR. 


77 


of  a  number  of  segments  of  copper  placed 
longitudinally  on  the  surface  of  a  cylinder, 
each  strip  bein^  insulated  from  the  adia- 

-L  O  J 


FIG.  14. — FORM  OF  COMMUTATOR. 

cent  strips  by  means  of  a  thin  plate  of 
mica.  The  commutator  strips,  segments,  or 
bars,  as  they  are  called,  are  connected  to 
the  free  ends  of  the  wires  which  are 


78 


ELECTRIC    STREET   RAILWAYS. 


soldered  into  the  clips  left  for  them.  Fig. 
15,  shows  a  completed  armature,  or  the 
appearance  of  the  armature  in  Figs.  12  and 


FIG.  15.— WOUND  ARMATURE. 

13,  when  the  process  of  connecting    and 
soldering   is  complete. 

It  now  remains  to  explain  the  manner  in 
which  the  electric  current  passing  through 
the  armature  causes  it  to  rotate.  When 


THE   MOTOR.  79 

the  current  enters  the  armature  conductors 
at  one  brush  and  circulates  around  the 
coils  of  wire  wrapped  on  its  surface,  it 
also  passes  through  the  coils  of  wire 
around  the  field  magnets.  By  these  means 
both  the  armature  and  the  field  poles  are 
rendered  magnetic,  and  it  is  to  the  mag- 
netic attractions  and  repulsions  that  take 
place  between  the  movable  armature  and 
the  fixed  field  poles,  that  the  rotation  of 
the  armature  and  the  mechanical  force  it 
develops  are  due.  Since,  however,  the 
form  of  electric  motor  employed  in  the 
street  car  is  very  compact  and  difficult  to 
understand,  it  will  be  preferable  first  to 
consider  a  few  simpler  types  of  electric 
motors. 

It  is  a  well  known  fact  that  when  two 
magnets  are  brought  near  together,  their 
unlike  poles  ;  i.  e.,  the  north  pole  of  one 


80  ELECTRIC    STREET    RAILWAYS. 

and  the  south  pole  of  the  other,  will 
attract,  while  their  like  poles  will  repel, 
so  that  if  one  of  the  magnets  be  free  to 
move,  it  will  come  to  rest  in  such  a  posi- 


FIG.  16. — ACTION  BETWEEN  MAGNET  AND  ACTIVE  COIL. 

tion  that  opposite  poles  are  adjacent.  A 
conductor  carrying  an  electric  current, 
acts  like  a  magnet,  so  that  if  a  magnet  be 
approached  to  an  active  coil  of  conductor ; 
i.  e.,  a  coil  carrying  a  current,  as  shown  in 
Fig.  16,  an  attraction  will  take  place  be- 
tween the  unlike  pole  of  the  magnet  and 
the  active  coil.  In  the  case  of  the  coil  of 


THE   MOTOR.  81 

insulated  wire,  shown  in  Fig.  16,  the  faces 
of  the  coil  become  magnetic,  as  marked  at 
S  and  N.  If  the  direction  of  the  current 
through  the  coil  be  reversed,  the  polarity 
of  the  coil  will  be  reversed,  so  that,  if  the 
coil  were  free  to  move,  it  would  turn 
around  and  present  its  opposite  end  to  the 
magnet ;  or,  if  prevented  from  doing  this, 
would  be  repelled  bodily  by  the  magnet. 

If  now  the  coil,  instead  of  being  sus- 
pended by  the  two  wires  which  carry 
the  current  into  and  out  of  it,  is  placed 
as  shown  in  Fig.  17,  that  is,  suspended 
flat  and  horizontally  in  the  position 
a  b  c  d,  by  the  two  wires  before  the 
north  pole  JV,  of  the  bar  magnet,  then,  as 
soon  as  a  sufficiently  powerful  current  is 
passed  through  the  coil,  it  will  set  itself  at 
right  angles  to  the  magnet  into  the  posi- 
tion a  b'  c'  d',  as  shown  by  the  dotted 


82  ELECTRIC    STREET   RAILWAYS. 

lines.  If  the  current  through  the  coil  be 
reversed,  the  coil  will  turn  around  and 
present  its  opposite  face  to  the  magnet. 
This  action  can  be  intensified  by  employ- 


FIG.  17.— DEFLECTION  OF  ACTIVE  COIL  BY  MAGNET. 

ing  two  bar  magnets  with  opposite  poles 
at  j^and  xSJ  as  shown  in  Fig.  18 ;  for,  each 
magnet  attracts  the  opposite  face  of  the 
coil.  By  corn bining  the  two  bar  magnets 
into  a  single  horseshoe  magnet  in  the 
manner  shown  in  Fig.  19,  the  action  on 


THE   MOTOR. 


83 


the  coil  can  be  rendered  still  more  power- 
ful. 

In  the  simple  form  of  apparatus  shown 
in  Figs.  17  to  19,  the  coil  has  been  sup- 


FIG.  18. —DEFLECTION  OF  ACTIVE  COIL  BY  OPPOSITE 
POLES  OF  Two  MAGNETS. 

ported  in  air.  If,  however,  the  coil  be 
wound  upon  a  cylinder  of  iron,  as  shown 
in  Fig.  20,  the  magnetic  power  with  which 
it  tends  to  rotate  is  very  much  increased. 
Moreover,  instead  of  employing  a  perman- 
ent horseshoe  magnet,  we  may  wind  a.  coil 


84 


ELECTRIC    STREET   RAILWAYS. 


of  insulated  wire  C  C,  around  the  soft  iron 
horseshoe  magnet  core,  shown  in  Fig.  20? 
and  by  passing  an  electric  current  through 
this  wire  we  may  obtain  a  more  powerful 


FIG.  19.— DEFLECTION  OF  ACTIVE  COIL  BY  HORSESHOE 
MAGNET. 

magnet  than  would  be  possible  with  any 
permanent  magnet  of  steel.  By  this 
means  we  obtain  a  still  more  powerful 
electromagnetic  twist  or  pull,  technically 


THE   MOTOR. 


85 


called    the   torque,   when    the   current    is 
allowed  to  pass  through  the  armature  coil. 

It  is  evident  that  in  the  preceding  cases 


FIG.  20. — DEFLECTION  OF  ACTIVE  COIL  WOUND  ON  IRON 
CORE  BY  ELECTROMAGNET. 

the  motion  of  the  coil  will  cease  as  soon  as 
it  sets  itself  at  right  angles  to  ibhe  line 
joining  the  magnetic  poles.  If,  however, 
the  current  in  the  coil  could  be  automati- 


86  ELECTRIC   STREET   RAILWAYS. 

cally  reversed;  i.  e.,  changed  in  direction, 
as  soon  as  this  position  was  reached,  the 
armature  would  turn  round,  or  rotate, 
through  half  a  revolution,  when  it  would 
again  come  to  rest  at  right  angles  to  the 
line  joining  the  poles  ^VJ  S.  The  device, 
whereby  the  direction  of  the  current 
through  the  coils  is  automatically  reversed 
every  time  that  the  coil  sets  itself  in  the 
neutral  or  dead  position,  so  as  to  ensure 
another  half  rotation,  is  called  a  com- 
mutator,  because  it  commutes  or  changes 
the  direction  of  current  in  the  coils  at  the 
desired  moment. 

Early  forms  of  electric  motors  employed 
only  a  single  coil  on  the  armature,  as 
represented  in  Fig.  20,  but  later  forms 
invariably  employ  a  number  of  coils  dis- 
posed at  uniform  angular  distances  around 
the  surface  of  the  armature  so  as  to  main- 


THE   MOTOR. 


87 


tain   the   twisting   power   or   torque   uni- 
form  in   all   positions. 

The   continuous-current   electric   motor, 


FIG.  21.— STATION AKY  ELECTRIC  MOTOR. 

as  in  actual  use  on  street  cars,  consists  sub- 
stantially of  a  suitable  combination  of  the 
parts  just  described;  namely,  of  the  anna- 


88  ELECTRIC    STREET    RAILWAYS. 

ture,  of  the  field  magnets  and  their  poles, 
and  of  the  commutator.  A  practical  form 
of  stationary  electric  motor  is  shown  in 
Fig.  21,  where  N  and  /SJ  are  the  poles 
of  a  powerful  electromagnet  wound  with 
many  turns  of  insulated  wire,  and  ^4, 
the  armature,  which  rotates  between  these 
poles.  C\  is  the  commutator  upon  which 
the  brushes  B,  B,  rest  in  such  a  manner 
that,  by  the  rotation  of  the  armature,  the 
direction  of  current  in  the  loops  of  wire  is 
changed  at  the  moment  required  to  ensure 
a  continuous  rotation. 

Motors  are  made  in  a  great  variety  of 
forms.  For  example,  instead  of  having  only 
two  poles,  four  or  more  poles  may  be  em- 
ployed. Thus  Fig.  22,  shows  a  form  of 
four-pole  or  quadripolar  motor,  with  its 
four  magnetizing  coils  N,  /SJ  N,  8,  pro- 
vided to  produce  the  four  poles.  In  this 


THE   MOTOR. 


89 


particular  case  four  sets  of  brushes  B,  B, 
are  employed,  of  which  only  three  are 
visible  in  the  cut.  The  armature  A, 


FIG.  22. — STATIONARY  QUADRIPOLAR  MOTOR. 

revolves  in  the  space  between  the  four 
poles,  and  the  current  is  supplied  to  this 
armature  from  the  brushes  B,  B,  through 


90  ELECTRIC    STREET   RAILWAYS. 

the  commutator  M.     Here  the  field  frame 
F  F  F,  is  of  cast  iron. 

Street-car  motors  are  almost  always  of 
the  quadripolar  type.  Owing  to  the  fact 
that  these  motors  have  a  very  small  space 
allotted  them  under  the  car,  and  are  re- 
quired to  be  very  light,  the  four  magnet 
poles  are  as  short  as  possible,  and  the  field 
frame,  instead  of  being  made  of  cast  iron, 
is  of  soft  cast  steel,  which  is  much  more 
advantageous  from  a  magnetic  point  of 
view.  In  the  motor  of  Fig.  11,  there  are 
four  poles,  two  only  of  which,  the  upper 
and  lower,  are  wound  with  coils  of  wire. 
The  poles  on  the  side  being  unwound  or 
being,  as  they  are  sometimes  called,  conse- 
quent magnetic  poles.  Fig.  23,  shows  the 
castings  for  another  form  of  quadripolar 
street-car  motor.  In  this  case,  each  of  the 
four  poles  -ZVJ  S,  N,  S,  is  surrounded  by  a 


THE   MOTOE. 


91 


magnetizing  coil,  and  the  whole  field  frame 
F F F,  is  of  cast  steel.  In  order  to  permit 
access  to  the  interior  of  the  field  frame,  it 


Q 


FIG.  23. — FIELD-FRAME  CASTINGS  OF  QUADRIPOLAR 
STREET-CAR  MOTOR. 

is  made  in  halves  and  the  upper  is  movable 
on  a  hinge  P.  The  armature  for  this 
motor  is  shown  in  Fig.  24  in  three  succes- 
sive conditions.  At  -4,  is  seen  the  un- 


92  ELECTRIC    STREET   RAILWAYS. 

wound  core  composed  of  sheets  of  iron 
punched  with  radial  teeth,  so  as  to  form, 
when  assembled,  a  compact  cylinder  with 
grooves  or  slots  as  shown.  At  J5,  the 


FIG.  24. — ARMATURE  FOR  MOTOR  OF  FIELD' FRAME  IN 
FIG.  23. 


insulated  conductors  have  been  placed  in 
these  grooves  ready  for  connection  to  the 
commutator  at  the  distant  end  of  the  core, 
while  at  C9  the  finished  armature  is  shown. 
The  appearance  of  a  similar  motor,  after 
being  assembled,  is  shown  in  Fig.  25. 
Here  A,  is  the  armature  geared  to  the  main 


THE   MOTOR. 


93 


axle  through  reducing  gear,  covered  by  the 
gear  cover  G  G.    B,  B,  are  two  brushes, 


FIG.  25. — ASSEMBLED  MOTOR  OPEN  FOR  INSPECTION. 

the  armature  winding  being  such  that  only 
two  brushes  need  to  be  employed.  This 
is  the  plan  generally  adopted  with  street- 
car motors,  while  stationary  quadripolar 


OF  THE 

NTIVERSITT 


94 


ELECTRIC   STREET    RAILWAYS. 


machines  usually  employ  four  brushes  or 
sets  of  brushes,  as  shown  in  Fig.  22.  N,  S, 
are  the  two  poles  in  the  upper  half  of  the 
field  frame,  each  being  surrounded  by  a 


FIG.  26. — COMPLETED  STREET-CAR  MOTOR. 

magnetizing  coil.  The  completed  motor, 
closed  and  ready  for  suspension,  is  shown 
in  Fig.  26.  Here  J57  shows  one  set  of 
brushes  protected  from  dust  and  mud  by 
the  shell  £  F  F,  is  the  field  frame,  G  6f, 


THE   MOTOE. 


95 


the  gear  cover.  A,  the  armature  shaft 
and  Jiy  the  truck-wheel  shaft.  C\  C,  C, 
the  terminals  of  the  motor  from  which 
wires  lead  to  the  controller  or  car  switch. 


FIG.  27. — BRUSH  HOLDER. 


A  form  of  brush  holder  employed  in  the 
motor  of  Fig.  11,  is  shown  in  Fig.  27. 
This  brush  holder  is  of  metal  and  is  clamped 
in  the  slot  C,  to  its  supporting  frame 


96  ELECTRIC    STREET   RAILWAYS. 

through  which  it  receives  the  electric  cur- 
rent. The  brush  slides  freely  in  the  guides 
(r,  G.  The  brush  being  composed  of  a 
rectangular  block  of  carbon,  the  arm  A, 
pivoted  at  JP,  maintains  a  uniform  pressure 


FIG.  28. — CARBON  BRUSH. 

at  the  back  of  the  brush  under  the  tension 
of  the  spiral  spring  St  thus  pressing  the 
brush  against  the  surface  of  the  "commuta- 
tor beneath.  The  arm  A,  can  be  with- 
drawn, and  the  brush  lifted,  by  pulling 
with  the  finger  upon  the  tongue  D.  A 
form  of  such  brush  is  shown  in  Fig.  28. 


OP  THE 

MDTKI.VERSITT 


CHAPTER  V. 

CAES  AND  CAR  TRUCKS. 

A  STREET  car,  as  it  appears  on  the  street, 
is  composed  of  two  distinct  parts ;  namely, 
the  car  body,  or  the  enclosed  space  for  the 
passengers,  and  the  car  truck,  or  the  part 
upon  which  the  car  body  rests.  Limiting 
our  present  consideration  to  the  car  truck, 
we  find  that  this  consists  generally  of  a 
frame  resting  upon  the  axles  of  the  wheels, 
through  journal  boxes. 

There  are  three  methods  of  supporting 
car  bodies  on  trucks ;  viz., 

(1)  By  the  use  of  a  single  rigid  truck 
Avith  four  wheels  and  two  axles,  the  axles 

97 


98  ELECTRIC    STREET    RAILWAYS. 

remaining  sensibly  parallel  in  all  positions 
of  the  car,  whether  on  curves  or  on  straight 
tracks. 

(2)  By  the  use  of  two  trucks,  one  at 
each  end  of  the  car.    In  this  case  the  car  is 
usually  supported   upon  the  swivel  centre 
of  each  truck. 

(3)  By  t-lis  use  of  three  trucks,  the  car 
being  supported  on   the  end    trucks,  and 
the  centre  truck  being  movable,  so  that  the 
car    axles   are    only    parallel    en    straight 
tracks,  and  are  radial  on  curves. 

A  single  truck  is  commonly  used  for 
short  cars  and  the  double  or  triple  truck 
for  long  cars. 

Fig.  29,  shows  a  particular  form  of 
single  truck.  F,  F,  F,  are  solid  forged 
side  frames.  B,  B,  are  the  journal  boxes, 
in  which  the  axles  run,  and  on  which  the 


CARS   AND   CAR  TRUCKS.  99 

weight  of  the  car  rests,  through  the  double 
spiral  springs  8,  S.  The  car  body  is  sup- 
ported on  the  steel  beams  B ',  B ',  which,  in 
their  turn,  rest  upon  the  side  frames 
through  the  four  spiral  springs,  and  the 


. 

FIG.  29.— SINGLE  TRUCK. 

two  elliptical  springs  on  each  side.     The 
wheels  are  provided  with  brake  shoes  L,  L. 

A  form  of  truck  for  a  double-truck  car 
is  shown  in  Fig.  30.  Here  the  motor  is 
mounted  so  as  to  drive  the  left-hand  axle, 
and  the  weight  of  the  car  is  so  disposed 
upon  the  truck  as  to  throw  the  principal 
share  of  the  weight  upon  this  pair  of 


100 


ELECTRIC   STREET   RAILWAYS. 


wheels  in  order  to  provide  sufficient  trac- 
tion and  prevent  the  rotation  of  the  motor 
from  causing  the  wheels  to  slip. 

Fig.  31,  shows  another  form  of  truck  for 
a  double-truck  car  called  a  maximum  trac- 


FIG.  30. — TRUCK  OF  DOUBLE-TRUCK  CAR. 


tion  truck.  This  truck  has  two  axles,  and 
two  pairs  of  wheels  of  different  diameters. 
The  motor  is  suspended  in  such  a  manner 
as  to  drive  the  larger  pair,  nearly  9/10ths 
of  the  weight  of  the  car  being  distributed 


CARS    AND    CAR   TRUCKS. 


101 


upon   these   wheels   so   as   to  obtain  the 
maximum   tractive   effort. 


Fig.   32,    shows  a   triple-truck    support, 
called  a  Robinson  radial  truck.     Here  the 


FIG.  31. — MAXIMUM  TRACTION  TRUCK. 

car  is  supported  upon  the  centres  of  the 
end  trucks  in  such  a  manner  that  these 
may  swivel  freely,  carrying  the  middle 
truck  between  them.  Fig.  33  illustrates 
the  action  of  these  trucks  when  going 
around  a  curve.  It  will  be  seen  that  the 
middle  truck  is  pulled  over  to  that  side  of 


102 


ELECTRIC    STREET   RAILWAYS. 


the  car  body  which  is  on    the   outside  of 
the  curve.     The  advantage  of  double  and 


FIG.  32. — ROBINSON  RADIAL  TRUCK. 

triple  trucks  is  considerable  with  long  cars, 
but  for  short  cars  they  are  usually  con- 
sidered unnecessary,  although  they  save 
some  power  and  wear  going  around  curves. 


FIG.  33.— ACTION  OP  RADIAL  TRUCK. 

The  appearance  presented  by  a  single- 
truck  car  is  illustrated  in  Fig.  34,  which 


I 


104  ELECTRIC   STREET   RAILWAYS. 

represents  a  car  body  21  feet  long  and  28 
feet  in  length  over  all,  with  a  width  over 
wheels  of  6  feet,  a  total  width  over  all  of 
7  1/2  feet,  and  capable  of  seating  30 
persons.  The  truck  weighs  without  mo- 
tors 3,500  pounds,  and  the  body  5,250 
pounds,  making  a  total  weight,  without 
motors  or  passengers,  of  8,750  pounds. 
Fig.  35  shows  a  double-truck  car.  The 
car  body  is  25  feet  long,  and  33  feet  over 
all.  The  width  over  wheels  6  feet,  and 
over  all  7  1/2  feet.  This  car  will  seat  36 
persons.  The  weight  of  the  truck  with- 
out motor  is  5,200  pounds,  and  the  body 
5,850,  making  a  total  weight,  without 
motors  or  passengers,  11,050  pounds. 

A  form  of  journal  boos  is  shown  in  Fig. 
36.  Here  the  lid  Z,  can  be  moved  aside 
for  examination,  or  for  filling  the  box.  The 
entire  box  is  dust  tight.  The  side  frames 


106  ELECTRIC    STREET   RAILWAYS. 

are  clamped  to  and  riveted  in  the  grooves 
£,  B,  so  that  the  weight  of  these  frames, 
and,  therefore,  the  entire  weight  of  the  car 


FIG.  36. — FORM  OP  JOURNAL  Box  AND  SUPPORT. 

pulls  down  upon  the  yoke  A,  and  presses 
the  double  spiral  spring  S,  upon  the  box 
L.  The  double  spiral  springs  on  all  the 


CARS   AND   CAR  TRUCKS. 


107 


boxes,  therefore,  bear  the  entire  weight  of 
the  car.     Fig.  37,  shows  a  cross-section  of 


FIG.  37. — SECTION  OF  Box  SHOWN  IN  FIG.  36. 

these  journal  boxes  taken  through  the  axis 
of  the  shaft.  A,  is  the  axis,  B,  B,  the 
brasses  from  which  the  weight  is  trans- 


108  ELECTRIC   STREET  RAILWAYS. 

mitted  to  the  axle,  W,  is  the  mass  of  lubri- 
cating material,  S,  the  double  spiral  spring 
supporting  under  compression  the  yoke  Y. 
P,  is  the  spring  packing  faced  with 
leather  to  keep  out  dust.  J?,  is  a  repair 
piece  which  is  marked  C\  in  Fig.  36.  This 
repair  piece,  when  removed  by  withdraw- 
ing two  bolts,  permits  the  frame  to  be 
lifted  clear  of  the  axles. 

Wheels  for  electric  street  cars  are  usu- 
ally 30  inches,  33  inches  or  36  inches  in 
diameter,  and  weigh  from  300  to  400 
pounds  each.  The  tread  of  the  wheel ; 
i.  e.,  its  running  face,  is  usually  chilled  to 
a  depth  of  1/2  or  3/4  inch  to  improve  its 
wearing  qualities.  A  good  wheel  should 
run  30,000  miles.  Wheels  are  usually 
forced  upon  their  axles  by  hydraulic  pres- 
sure, but  in  some  cases  they  are  bolted  to 
collars  on  the  axle,  which  collars  are  them- 


CARS   AND   CAR  TRUCKS.  109 

selves  forced  hydraulically  on  the  axle. 
There  are  two  types  of  wheel,  the  open 
and  the  dosed.  Fig.  38,  shows  a  form  of 


FIG.  38.— OPEN  CAR  WHEELS. 

open  wheel  and  Fig.  39,  a  form  of  closed 
wheel. 

Motors  may  be  mounted  on  the  trucks 
in  several  ways.  The  most  usual  method 
is  to  support  each  motor  partly  on  the 


110          ELECTRIC   STREET   RAILWAYS. 

axle  it  drives,  and  partly  on  a  cross  beam 
extending  between  the  side  frames.  This 
is  shown  in  Fig.  40,  where  the  motor  J/  of 


FIG.  39.— CLOSED  CAR  WHEEL. 

the  type  shown  in  Fig.  11,  is  supported  on 
the  cross  beam  B  J3,  which  is  itself  sup- 
ported from  the  side  frames  by  the  spiral 
springs  s,  s.  These  spiral  springs  are,  of 
course,  employed  to  reduce  the  vibration, 
or  jolting  of  the  motor,  when  running  over 
an  uneven  track.  The  cross  beams,  instead 


CARS   AND   CAR  TRUCKS. 


Ill 


of  passing  beneath  the  motor  may  pass 
above  it,  or  on  a  level  with  its  surface,  as 
shown  in  Fig.  41,  where  the  beam  B  B. 


FIG.  40. — METHOD  OF  MOTOR  SUSPENSION. 

rests  above  the  spiral  springs  instead  of 
beneath  them.  In  Fig.  42,  another  method 
is  shown  where  the  beams  B  B,  from  which 
the  motor  is  suspended,  are  longitudinal 
and  rest  on  spiral  springs,  which  them- 
selves rest  upon  cross  beams  secured  to 


112  ELECTRIC    STREET   RAILWAYS. 

the  side  frame  of  the  truck.  In  this  case 
very  little  of  the  motor's  weight  comes 
immediately  upon  the  driving  axle,  almost 


FIG.  41. — METHOD  OF  MOTOR  SUSPENSION. 


all  being  transmitted  to  the  axle  from  the 
side  frames. 


A  plan  and  side  view  of  the  ordinary 
motor  suspension  in  a  single-truck  car  are 
shown  in  Fig.  43,  where  the  two  motors 
M,  J/,  are  seen,  each  connected  to  one  of 
the  main  axles  through  the  gear  G,  6r. 
The  motors  are  suspended  partly  upon  the 
main  axles  and  partly  upon  the  cross 


CARS   AND   CAR  TRUCKS. 


113 


beams  B  B,  and  B  B,  the  four  wheels 
TFJ    W,   W,   W,  are  thus   directly  driven 
from  the  motor  through  the  gears. 


FIG.  42.— METHOD  OF  SUSPENDING  MOTOR. 

The  gearing  employed  in  connection 
with  the  electric  street  railway  cars,  is 
effected  by  means  of  a  steel  pinion  upon 
the  armature  shaft,  such  as  shown  in 
Fig.  44.  This  pinion  has  14  teeth,  which 
are  mechanically  cut  so  as  to  mesh  freely 


114 


ELECTRIC  STREET  RAILWAYS. 


into  the  teeth  of  the  gear  wheel  fixed 
rigidly  upon  the  car  axle.  This  gear  wheel 
is  usually  made  of  cast  iron  in  two  parts, 


.    rib  „ 


^   rfti    ^ 


FIG.  43.— PLAN  AND  SIDE  ELEVATION  OF  MOTOR 
SUSPENSION. 

as  shown  in  Fig.  45.  The  gear  wheel 
shown  has  67  teeth.  The  ratio  of  speed 
reduction  between  the  motor  and  the  car 

nH 

axle  is,  therefore,  in  this  case,  jj  =  4.786. 
In  other  words,  the  car- wheel  axle  runs 


CARS   AND   CAR  TRUCKS.  '  115 

4.786  times  more  slowly  than  the  motor 
shaft.  If  we  consider  a  car  with  33  inch 
wheels,  the  circumference  of  the  wheels 
will  be  103.67  inches  or  8.639  feet.  This 
will  be  the  distance  through  which  the 
car  will  move  for  one  complete  revolution 


FIG.  44. — ARMATURE  PINIONS. 

of  the  wheels.  A  speed  of  1  mile  per  hour 
over  the  track,  is  a  speed  of  88  feet  per 
minute,  and,  therefore,  a  rotatory  speed  of 
88  -*•  8.639  =  10.186  turns  per  minute  of 
the  car  wheels.  The  speed  of  the  motor 
armature  will  be  4.786  times  this  amount 
or  48.76  turns  per  minute.  Consequently, 
for  every  mile  per  hour  that  the  car  runs, 


116  ELECTRIC   STREET   RAILWAYS. 

the  motors   will    make    48.76   revolutions 
per  minute.     Thus  at  10  miles  per  hour 


FIG.  45.— AXLE  GEARS. 

they  will  each  make  487.6  revolutions  per 
minute. 

Pinions  are   sometimes   constructed   of 
hot  pressed  steel.     Thus  Fig.  46,  shows  a 


CARS   AND    CAR   TRUCKS.  117 

steel  cylinder  before  pressing  and  the  com- 
pleted pinion  wheel  pressed  from  such  a 
cylinder. 


AFTER. 

FIG.  46.— HOT-PRESSED  PINION,  BEFORE  AND  AFTER 
PRESSING. 

The  motors  which  we  have  hitherto 
considered  are  all  single-reduction  motors^ 
that  is  to  say,  there  is  only  one  reduction 


118          ELECTRIC   STREET   RAILWAYS. 

in  speed  effected  by  gearing  between  the 
motor  axle  and  the  car  axle.  During  the 
early  application  of  the  street  car  motor  it 
was  very  difficult  to  obtain  good  slow-speed 
motors  of  light  weight,  and,  consequently, 


FIG.  47.— DOUBLE-REDUCTION  MOTOR. 

the  expedient  was  adopted  of  reducing  the 
speed  down  to  that  required  for  the  car 
axle  by  a  double  reduction.  Figs.  47  and 
48  show  a  type  of  double-reduction  motor. 
In  each  figure,  A,  is  the  armature  bearing 


CARS   AND   CAB  TRUCKS. 


119 


through  which  the  axle  passes.  B,  is  an 
intermediate  shaft  carrying  a  double-gear 
wheel  at  on£  end  as  shown  in  Fig.  48, 
meshing  with  a  double  pinion  on  the  arma- 
ture shaft ;  while,  at  the  other  end,  it 


FIG.  48. — DOUBLE-REDUCTION  MOTOR. 

carries  a  pinion  meshing  into  a  gear  wheel 
on  the  car-wheel  shaft  passing  through 
the  bearing  C.  In  this  type  of  machine 
the  double  redaction  in  speed  varies  from 
9  to  19,  according  to  the  size  of  the  motor 
and  requirements  of  speed  and  power. 
In  recent  times  the  double-reduction  motor 


OF  THE  v 

•0HIVERSI1 
CALIF? 


120  ELECTRIC   STREET   RAILWAYS. 

has  almost  disappeared.  One  difficulty 
with  the  double-reduction  motor  was  the 
noise  made  by  the  rapidly  rwnning  arma- 
ture pinion.  To  reduce  this,  rawhide 
pinions  ;  i.  e.,  pinion  wheels  made  up  of 


FIG.  49.  —RAWHIDE  PINION. 

discs  of  rawhide,  cut  into  the  proper 
shape,  assembled  and  clamped  together, 
were  employed,  of  the  type  shown  in  Fig. 
49.  The  lifetime  of  such  rawhide  wheels 
was  never  very  extended. 


CARS   AND    CAR   TRUCKS. 


121 


The  life  of  steel  and  iron  gearing 
depends  largely  upon  the  care  with  which 
the  dust  is  excluded  from  them.  In  prac- 


FIG.  50.— GEAR  CORES. 


tice  an  increased  life  is  ensured  by  enclosing 
the  gear  in  a  dust-proof  gear  cover,  as 
shown  in  Fig.  50. 


122          ELECTRIC   STREET   RAILWAYS. 

It  is  evident  that  for  safety  of  running 
cars  through  crowded  thoroughfares,  it  is 
absolutely  necessary  to  be  able  to  stop  a 
car  with  certainty  in  a  short  distance.  In 
order  to  effect  this,  various  forms  of  brake 
mechanism  are  employed.  These  are  either 
operated  by  hand,  or  by  the  electric  current. 
Pneumatic  car  brakes  have  not  come  into 
any  extended  use  up  to  the  present  time 
for  this  purpose,  since  they  require  the 
addition  of  a  pneumatic  compressor  to  the 
car  equipment. 

A  common  form  of  lever  brake,  operated 
by  hand,  from  either  end  of  the  car,  is 
shown  in  Fig.  51  and  also  in  Fig.  43.  R, 
H',  are  the  projecting  rods  to  one  or  other 
of  which  the  power  is  applied  by  a  chain 
and  handle.  Fig.  52  shows  the  ordinary 
brake  handle  at  the  car  platform.  By 
rotating  this  handle  the  chain  C,  is  wound 


CARS    AND   CAR   TRUCKS.  123 

upon  the  handle  shaft,  thus  hauling  upon 
the  brake  rod  H'.  .P,  is  a  pawl  engaging 
with  the  pinion  wheel  on  the  brake  handle 
shaft  so  as  to  hold  or  release  the  brake  as 
desired.  Fig.  51,  shows  that  when  one  of 


FIG.  51. — HAND  BRAKE  MECHANISM. 

the  brake  rods,  say  H,  is  pulled  by  the 
chain,  the  lever  X,  is  drawn  forward  and 
by  the  action  of  the  short  bar  C,  or  brake 
beam  clevis,  the  brake  beam  S  is  forced 
backwards,  so  as  to  cause  the  brake  shoes 
H,  H,  to  press  against  the  treads  of  the 
wheel  W,  W.  At  the  same  the  brake 


124         ELECTRIC    STREET    RAILWAYS. 

frame  L  R  R  R  R  L',  is  forced  forward, 
thus  drawing  the  other  brake  beam  B1^ 
forward,  and  causing  the  shoes  H ',  H ',  to 
bear  against  the  tread  of  the  wheels 


FIG.  52.— BRAKE  HANDLE  AND  CHAIN. 

W  W'.  As  soon  as  the  tension  is 
released  from  the  brake  rod,  the  brake 
frame  L  R  R  R  R  L',  releases  and 
throws  the  shoes  off  the  wheels. 


CARS   AND   CAR  TRUCKS.  125 

When  the  arm  is  applied  to  the  brake 
handle  H,  Fig.  52,  the  pull  so  delivered  is 
multiplied  by  the  leverage  of  the  handle 
over  the  chain.  This  pull  being  delivered 
at  R',  is  again  multiplied  by  the  leverage 
of  the  brake  lever  L.  The  combined 
leverage  of  the  brake  staff  and  brake  lever 
is  usually  about  50,  so  that  a  pull  of  100 
pounds  weight,  delivered  horizontally  at 
the  brake  staff  handle,  represents  a  pull  of 
about  5,000  pounds  delivered  at  all  four 
brake  shoes,  or  about  1,250  pounds  total 
pressure  between  each  shoe  and  the  wheel 
it  grips.  The  effect  of  this  pressure  is  to 
produce  about  l/8th  of  the  pressure  as  a 
frictional  retarding  force,  so  that  if  1,250 
pounds  pressure  be  supplied  to  each 
wheel,  the  retarding  drag  applied  at  the 
wheel  tread  is  about  160  pounds. 

The   turnbuckle   T  T,  enables  the  play 


126  ELECTRIC    STREET   RAILWAYS. 

of  the  brake  rods  and  brake  arm  to  be  ad- 
justed so  that  any  unnecessary  delay  in 
applying  the  brakes  may  be  avoided. 

A   form    of    electric    car    brake,  which 


FIG.  53. — ELECTRIC  BRAKES  MOUNTED  ON  STREET  CAR 
TRUCKS. 

promises  to  come  into  extended  use,  is 
represented  in  Fig.  53.  A  truck  is  here 
represented  with  two  motors  M,  M,  in 
place,  of  the  same  character  as  shown  in 
Fig.  11.  In  addition  to  the  ordinary  hand 
brake  mechanism  operating  through  the 


CARS   AND   CAR  TRUCKS  127 

brake  rods  r,  r,  the  brake  levers  I,  I' 
the  brake  beam  m,  and  the  shoes  5,  5, 
there  is  supplied  an  electric  brake  B,  on 
each  car  axle.  This  brake  is  in  two 
parts ;  namely,  a  cast  iron  disc  (7,  rigidly 
keyed  to  the  car  wheel  axle,  and,  therefore, 
revolving  with  the  car  wheel,  and  a  cir- 
cular shoe  or  compact  electromagnet  D, 
facing  C,  clamped  to  the  motor  and  frame 
of  the  car,  and,  consequently,  not  rotating 
whether  the  car  be  running  or  at  rest. 
When  the  car  is  running  there  is  no  fric- 
tion between  the  shoe  D,  and  the  disc  C. 
As  soon  as  it  is  desired  to  stop  the  car, 
the  trolley  circuit  is  first  broken  at  the 
trolley  switch  by  the  motorman,  thus  cut- 
ting off  the  power  from  the  line.  As 
soon  as  this  is  done  the  motors  which  are 
still  running  by  the  momentum  of  the  car, 
act  as  ordinary  dynamos,  and  are  capable 
of  furnishing  a  temporary  electric  current 


128          ELECTRIC    STREET   RAILWAYS. 

as  soon  as  a  circuit  is  closed  to  their 
E.  M.  F.  The  coil  of  insulated  wire  in  the 
interior  of  the  magnet  shoes  D,  D,  of  the 
brakes  are  placed  in  circuit  with  the  motor 
armatures  so  as  to  receive  this  current. 

Under  these  circumstances  a  powerful 
electromagnetic  attraction  occurs  between 
the  shoes  D,  D,  and  their  iron  discs  C,  C, 
tending  to  clutch  them  together  and  stop 
the  wheels.  The  faster  the  car  is  running 
at  the  moment  these  brakes  are  applied, 
the  more  powerful  is  the  current  that  is 
generated  by  the  motors  acting  as  dynamos, 
and,  consequently,  the  higher  the  brake 
action. 

There  are  two  methods  of  controlling 
this  brake,  the  first  automatic,  and  the  sec- 
ond under  the  control  of  the  motorman. 
The  braking  power,  if  uncontrolled,  would 


CARS    AND    CAR   TRUCKS.  129 

be  so  great  that  the  wheels  would  be  in- 
stantly locked  and  would  skid  or  slide  on 
the  track.  An  automatic  switch  is  placed  in 
the  circuit  in  such  a  manner  that  the  cur- 
rent strength  from  the  motors  through  the 
brakes  is  limited  to  that  which  will  apply 
the  maximum  braking  power  without  per- 
mitting skidding  with  a  light  car.  More- 
over, the  braking  current  passes  through 
the  controller  to  be  subsequently  described, 
and  is  thus  regulated  in  strength  by  the 
raotormaD,  so  that  he  can  apply  the  elec- 
tric brake  either  suddenly ,  or  gradually,  as 
he  may  desire.  The  advantage  of  the  elec- 
tric car  brake  is  the  power  it  possesses,  the 
swiftness  with  which  it  can  be  applied,  and 
the  fact  that  it  is  independent  of  all  current 
taken  from  the  trolley  wire,  since  the 
moving  motors  supply  the  energy  needed. 
The  mechanism  can,  moreover,  be  attached 
to  any  car  without  great  expense,  while 


130  ELECTRIC    STREET   RAILWAYS. 

the  ordinary  brake  is  left  untouched  for 
use  in  cases  of  emergency.  A  special  ar- 
rangement is  made  to  lubricate  the  rotating 
surfaces  by  means  of  a  graphite  brush  car- 
ried in  the  shoes  J9,  D.  This  prevents  ex- 
cessive wear  and  heating;  for,  in  this  brake, 
the  retardation  is  very  largely  a  magnetic 
pull  rather  than  a  mechanical  friction,  and, 
in  this  way,  effective  brake  action  is 
secured  without  excessive  rubbing. 

When  the  rails  are  slippery,  by  reason  of 
a  thin  film  of  mud  or  frost,  an  application 
of  the  brake  is  apt  to  cause  adhesion  of  the 
shoe  to  the  brake  wheel,  and  a  skidding  or 
slipping  of  the  wheel  on  the  track,  instead 
of  an  adhesion  between  the  wheel  and  the 
track  and  a  slipping  of  the  brake  shoe  on 
the  wheel.  The  result  of  this  skidding  is 
to  wear  the  tread  of  the  wheel  at  the  point 
of  its  periphery  at  which  it  slips  along  the 


CARS   AND   CAR   TRUCKS.  131 

track,  whereas  in  the  normal  application  of 
the  brake,  this  wear  is  uniformly  distrib- 
uted over  the  entire  wheel  surface  against 
the  brake  shoe.  Under  these  conditions 
the  wheel  tends  to  flatten  at  the  point  of 
skidding,  and  once  a  depression  is  formed, 
there  is  a  continual  tendency  to  increase 
the  amount  of  flattening.  Flat  wheels  are 
not  only  difficult  to  brake  properly,  but 
produce  an  uneven  jarring  motion  very  dis- 
agreeable to  the  passengers.  In  order  to 
increase  the  adhesion  between  the  wheel 
and  track,  so  as  to  be  greater  than  that 
between  the  brake  shoe  and  the  wheel,  sand 
is  sometimes  poured  upon  the  track  with 
the  effect  of  producing  a  greater  friction. 
Various  forms  of  sand  boxes  have  been  de- 
vised for  sprinkling  a  small  quantity  of 
sand  directly  beneath  the  wheel  on  the 
track  where  it  is  required.  One  of  these 
forms  is  shown  in  Fig.  54.  The  sand  box 


132 


ELECTRIC    STREET   RAILWAYS. 


S,  is  mounted  within  the  car  close  to  the 
platform.  The  motorman,  by  pressing  with 
his  foot  upon  the  foot-button  F,  depresses 
the  lever  L,  which  is  pivoted  at  P,  and 


FIG.  54.— SAND  Box. 

thus  causes  the  rod  H,  to  move  forward  in 
the  direction  of  its  length  against  the  ten- 
sion of  the  spiral  spring  G.  This  opens 
the  valve  outlet  and  allows  sand  to  pour 
through  the  tube  T,  upon  the  track 
beneath. 


CARS   AND   CAR  TRUCKS.  133 

On  the  truck  of  a  car  there  is  mounted  a 
car  body  familiar  to  all  our  readers.  These 
bodies  are  of  four  types ;  namely,  the  open 
or  summer  car,  the  closed  car,  the  converti- 
ble car,  and  the  double  decker.  The  latter 
is  not  in  use  on  overhead  trolley  lines. 


CHAPTER  VI. 

ELECTRIC  LIGHTING  AND  HEATING  OF  CARS. 

THE  advantages  possessed  by  electric 
lighting,  as  obtained  from  incandescent 
lamps,  are  so  evident,  that  this  method  of 
artificial  illumination  is  almost  invariably 
employed  in  trolley  cars.  The  current 
required  for  the  lighting  of  these  lamps  is, 
of  course,  taken  from  the  same  source 
which  drives  the  car,  that  is  to  say,  a 
special  circuit  is  taken  from  the  trolley  to 
the  track,  through  the  lamps  to  be  lighted. 
The  type  of  incandescent  lamp  employed 
varies  with  the  number  placed  in  the  car. 
If,  as  is  commonly  the  case,  there  are  five 
lamps,  three  in  the  centre  and  one  at  each 


134 


LIGHTING   AND   HEATING   OF   CARS.       135 


end,  they  are  connected  in  series,  so  that 
the  current  passes  successively  through 
each,  and  they  are  placed  in  a  special  cir- 
cuit directly  between  the  trolley  and  the 
track  as  represented  in  Fig.  55.  Here 

Tr 


k? 


L. 


ITk 

FIG.  55. — DIAGRAM  OF  LAMP  CIRCUIT  OP  CAR. 

the  wire  leading  to  the  trolley  wheel  is 
marked  Tr,  and  enters  the  switch  S,  from 
which  it  passes  through  the  nVe  lamps 
L<b  .Z/2,  X3,  L±,  1;^  in  succession,  finally  pass- 
ing to  the  track  T~k,  through  the  frame- 
work of  the  truck. 

In  this  case  since  the  total  pressure  be- 
tween  the   trolley  and   track   is  approxi- 


136  ELECTRIC   STREET   RAILWAYS. 

naately  500  volts,  and  there  are  five 
lamps  in  series,  the  drop  in  each  lamp  will 
be  100  volts,  the  current  strength  being 
about  2/3rds  ampere.  The  total  activity 
developed  in  the  lamps  will  be  roughly 
500  volts  X  2/3rds  ampere  =  333  watts, 
or  less  than  one- half  of  a  horse-power. 
When  nine  lamps  are  employed  to  light 
the  car,  in  three  clusters  of  three  each,  all 
nine  are  placed  in  one  series,  the  drop  in 

50 

each  lamp  being  approximately  -  -  =  55.5 

y 

volts.  The  current  strength  in  this  case 
will  be  a  little  more  than  1  ampere  and 
the  activity  in  the  lighting  circuit  will 
be  nearly  500  volts  x  1.1  amperes  =  550 
watts,  or  3/4ths  horse-power.  This  activity 
has  to  be  sustained  during  the  operation 
of  the  cars  at  night  time  whether  the  car 
be  running  or  not.  If  five  lamps  are 
employed,  each  lamp  must  be  made  for  a 


LIGHTING   AND   HEATING   OF   CARS.       137 

pressure  of  roughly  100  volts,  while  if 
nine  lamps  are  employed,  each  lamp  must 
be  made  for  a  pressure  of  roughly  55  volts. 


FIG.  56.— CAR  LAMP. 


Fig.  56  shows  a  common  form  of  lamp 
employed  in  street  cars.  Fig.  57  shows 
another  form  in  which  the  incandescing 
filament  is  anchored  or  supported  at  its 


138 


ELECTEIC   STREET   RAILWAYS. 


centre  for  the  purpose  of  preventing  the 
filament  from  being  injured  by  excessive 
vibration.  Incandescent  lamps  for  street 


FIG.  57. — RAILWAY  LAMP  WITH  ANCHORED  OR  NON- 
VIBRATING  FILAMENT. 

car  use  have  usually  an  efficiency  of  l/4th 
candle  per  watt ;  i.  e.,  when  operated  at 
the  pressure  for  which  it  is  designed,  it 


LIGHTING   AND   HEATING   OF   OAKS.       139 

gives  normally  l/4th  of  a  candle  per  watt 
of  activity  absorbed,  so  that  a  16  candle- 
power  lamp  would  require  normally  64 
watts. 


FIG.  58. — FORM  OP  FIXTURE  FOR  CAR  LAMP. 

A  common  form  of  lamp  fixture  is 
shown  in  Fig.  58  and  a  cluster  suitable  for 
three  lamps  is  shown  in  Fig.  59. 

A  form  of  switch  for  turning  the  car 
lamps  on  and  off,  is  shown  in  Fig.  60. 
This  switch  box  is  screwed  up  inside  the 


140  ELECTKIC    STREET   RAILWAYS. 

car  near  the  ceiling  and  has  a  projecting 
key  K,  for  turning  the  lamps  on  or  off. 
The  action  of  the  key  is  illustrated  by  the 
switch  shown  in  Fig.  61,  where  A  and  B, 


FIG.  59. — FORM  OF  THREE-LAMP  CLUSTER  FOR  CAR. 

are  the  binding  posts  connected  to  one 
side  with  the  trolley  wheel  and  the  other 
with  the  lamps.  On  turning  the  key  D, 
the  brass  piece  (7,  may  be  made  to  bridge 
metallically  across  between  the  posts  A 
and  B,  thus  closing  the  circuit  through  all 
the  lamps.  The  switch  box,  in  Fig.  60, 


LIGHTING   AND    HEATING   OF    CARS.       141 

also  contains  a  safety  fuse  or  cut-out. 
This  simple  device  consists  of  a  wire  of 
lead  or  other  alloy  that  will  melt,  and 
thus  automatically  break  the  circuit,  if  the 
current  becomes  excessive. 


FIG.  60. — SWITCH  AND  CUT-OUT  FOR  CAB  LAMPS. 

It  will  be  evident  that  for  every  16 
candle-power  incandescent  lamp  operated 
in  the  car,  about  64  watts  activity  will  be 
required;  or,  roughly,  1/1 2th  of  a  horse- 
power per  lamp  at  the  car,  which  may 
represent  say  l/8th  of  an  indicated  horse- 
power at  the  engine. 


142  ELECTRIC   STREET   RAILWAYS. 

When  street  cars  are  running  in  cold 
climates  the  artificial  heat  required  at  cer- 
tain seasons  of  the  year  may  be  obtaiped 
either  by  the  use  of  an  ordinary  coal  stove, 

D 


FIG.  61. — SWITCH  FOR  CAR  LAMPS. 

or  by  electric  heaters.  Although  the  coal 
stove  is  the  cheaper  of  the  two,  yet  it  pos- 
sesses several  inconvenient  features.  In 
the  first  place  it  occupies  useful  space ;  in 
the  second  place  it  requires  attention  and 
introduces  more  or  less  dust,  smoke  or  dirt 
into  the  car,  while  the  heat  which  it  gives 


LIGHTING   AND   HEATING   OF   CARS.       143 

is  principally  developed  in  the  upper  por- 
tion of  the  car,  the  air  near  the  floor 
remaining  comparatively  cold.  Moreover, 
some  time  is  required  to  start  a  fire  in 
a  stove. 

In  contrast  with  these  inconveniences, 
the  electric  heater  possesses  such  marked 
advantages,  that,  despite  its  extra  cost,  it 
has  come  into  use  for  the  heating  of  electri- 
cally propelled  cars.  When  an  electric 
current  passes  through  a  wire,  heat  is  de- 
veloped therein.  Thus,  we  have  already 
seen  that  when  a  current  passes  through  a 
trolley  wire,  a  certain  amount  of  power 
will  be  expended  in  heating  the  trolley 
wire.  Under  practical  conditions  the 
trolley  wire  will  never  get  sensibly  warm 
by  the  current  it.  carries  for  the  reason 
that  the  surface  it  freely  exposes  to  the 
air  is  so  great,  that,  taken  in  connection 


144 


ELECTRIC    STREET   RAILWAYS. 


with  its  mass,  the  comparatively  small 
amount  of  heat  developed  within  it  is 
rapidly  liberated.  If,  however,  the  same 
amount  of  electric  resistance  which  ex- 
ists in  a  mile  of  trolley  wire,  were  obtained 


FIG.  62.— HEATING  COILS  OP  CAB  HEATER. 

in  a  short  length  of  copper  or  iron  wire, 
then  the  same  amount  of  heat  would  be 
produced  in  a  much  smaller  mass  of  iron, 
having  a  greatly  reduced  surface,  with  the 
result  of  producing  a  much  higher  tem- 
perature in  the  wire. 

The  coils   of   wire  used  in  a  particular 
form  of  car  heater  are  shown  in   Fig.  62. 


LIGHTING   AND   HEATING   OF   CARS.       145 

Here  the  heating  coil  consists  of  galvanized 
iron  wire  which  is  wrapped  in  the  form  of 
a  close  spiral  and  then  placed  in  a  spiral 
groove  on  the  outside  of  a  porcelain  tube. 
This  construction  affords  a  great  length  of 
heating  coil  in  a  small  space,  so  supported 
as  to  prevent  the  coil  changing  its  form 
when  heated  and  yet  practically  permit- 
ting nearly  all  of  its  surface  to  give  off 
heat  to  the  surrounding  air.  In  the  heat- 
ing coil  shown  in  the  figure,  which  is  about 
3'  6"  long,  there  are  392'  of  wire ;  the  size 
of  wire  being  No.  20  A.  W.  G.  iron  wire, 
having  a  diameter  of  0.032",  or  32  mils. 
The  total  surface  exposed  by  the  coil 
in  a  single  heater  is  1.642  square  feet. 
The  coil  is  placed  in  a  metal  case,  so  pro- 
vided with  openings  as  to  permit  the  free 
flow  of  air  entering  at  the  bottom  of  the 
case  to  flow  around  the  heater,  come  in 
contact  with  the  heated  wire  and  to 


146  ELECTRIC    STREET   RAILWAYS. 

escape  through  a  grating  at  the  top. 
When  so  desired,  the  air  may  be  taken  in 
directly  from  the  outside  of  the  car.  The 
coil  in  its  metal  case,  ready  for  fastening 
in  position  below  a  seat,  is  represented  in 


FIG.  63.— ELECTRIC  CAR  HEATER. 

Fig.  63.  The  heater  is  sometimes  placed 
with  its  grating  flush  with  the  riser  be- 
neath the  seat.  In  this  case  the  form  of 
heater  is  that  shown  in  Fig.  64.  For  cars 
of  the  ordinary  size,  four  or  six  heaters  are 
employed ;  i.  <?.,  two  or  three  on  each  side 
of  the  car.  The  heaters  are  placed  in  the 


HEATING   AND   LIGHTING   OF   CARS.       147 

risers  of  the  seats  near  the  floor.  In  Fig. 
65  the  interior  of  a  car  is  shown  equipped 
with  six  heaters,  four  of  which  are  seen 
beneath  the  seats  at  the  points  A,  J3,  C\  D. 


CFrcrf  r-rrrTrrrrrj^ri-rc-:" 


FIG.  64.—  FORM  OF  ELECTRIC  CAR  HEATER. 

In  order  to  regulate  the  amount  of  heat 
required  to  meet  the  changes  in  tempera- 
ture, a  temperature-regulating  switch  is 
employed,  by  means  of  which  the  separate 
heaters  may  be  connected  in  series  or  in 
parallel  groups  between  the  trolley  and 
the  track,  or  by  means  of  which  one  or 
more  of  the  heaters  may  be  removed  at 
will.  By  this  means  the  amount  of  cur- 


. 

-Xf^C-t 
f       V^         OF  THE 

/UNIVERSITY 

^ 


148  ELECTRIC    STREET   RAILWAYS. 

rent  which  passes  through  the  heaters,  and, 
therefore,  the  amount  of  heat  they  develop 
can  be  adjusted.  When  the  switch  is 
turned,  so  as  to  place  all  the  heaters  in 
series,  the  resistance  in  the  heating  circuit 
is  greatest  and  the  heat  produced  is  least. 
When  all  the  heaters  are  employed  in  three 
parallel  groups  of  two  each,  the  maximum 
current  is  supplied  and  the  maximum  heat 
is  obtained. 

Fig.  66,  represents  the  interior  of  the 
temperature-regulating  switch,  by  which 
these  varied  connections  are  made.  Fig. 
67,  shows  the  exterior  appearance  of  the 
switch.  There  are  five  positions  of  this 
switch  when  the  current  is  passing  through 
it,  numbered  respectively,  1,  2,  3,  4  and  5, 
and  the  particular  position  is  indicated  by 
the  numeral  appearing  through  the  open- 
ing at  W,  in  the  switch  casing.  The 


I 


150 


ELECTRIC    STREET   RAILWAYS. 


switch  is  so  constructed  that  before  chang- 
ing from  one  number  to  another,  the  cir- 
cuit of  the  heaters  is  opened.  In  position 
5,  as  shown  in  the  figure,  the  full  current 


FIG.  66.— INTERIOR  TEMPERATURE-REGULATING  SWITCH 
(FIVE  INTENSITIES). 

strength  of  about  12  amperes  passes 
through  the  heater,  representing  a  total 
activity  of  about  500  volts  x  12  amperes  = 
6,000  watts  =  6  KW  =  8  HP  approxi- 
mately. This  activity  is  entirely  expended 
in  heating  the  wire,  and,  therefore,  in 


LIGHTING   AND    HEATING   OF   OAKS.      151 

warming  the  air  which  comes  in  contact 
with  the  wire.  Position  No.  1,  corre- 
sponds to  the  minimum  activity  and  allows 
about  2  amperes  to  pass  through  the 


FIG.  67.— EXTERIOR  TEMPERATURE-REGULATING  SWITCH. 

heater,  representing  a  total  activity  of 
about  500  volts  X  2  amperes  =  1,000 
watts  =  1  KW  =  11/3  HP,  approximately. 
In  practice,  it  is  found  that  in  cold 
weather  about  6  amperes  have  to  be  main- 
tained in  the  heaters,  representing  an 


152 


ELECTRIC    STREET   RAILWAYS. 


activity  of  roughly  3  KW.  The  cost  of 
producing  a  KW-lwur,  or  1,000  joules-per- 
second  for  3,600  seconds  =  3,600,000  joules, 


FIG.  68.— CAR  HEATER. 


varies  considerably  with  the  size  of  the 
electric  plant  supplying  the  current,  but, 
speaking  generally,  a  fair  average  may  be 
considered  as  being  1  1/2  cents  per  KW- 
hour,  so  that  the  expense  of  heating  the 
cars  electrically  during  severe  weather  may 
be  estimated  roughly  as  4  1/2  cents  per 
hour. 


LIGHTING   AND   HEATING   OF   CARS.       153 

Another  form  of  car  heater  and  its  en- 
closing case  is  shown  in  Figs.  68  and  69. 


FIG.  69. — CAR  HEATER,  DESIGNED  TO  ATTACH  TO  SEAT 
RISER. 

This     operates    on  practically    the    same 
principles. 


CHAPTER  VII. 

CONTROLLERS    AND    SWITCHES. 

IT  is  necessary  in  the  practical  operation 
of  a  street  car  to  place  both  its  speed  and 
the  direction  of  its  running  under  the  con- 
trol of  the  motorman.  Moreover,  the  ap- 
paratus employed  to  do  this  should  require 
for  its  operation  no  more  than  ordinary 
intelligence,  that  is,  should  be  capable  of 
being  operated  without  any  electrical  skill 
on  the  part  of  the  motorman.  On  electric 
trolley  cars,  as  is  well  known,  the  motorman 
controls  the  car  by  means  of  two  handles, 
the  right  hand  one  of  which  controls  the 
mechanical  brake  apparatus  and  the  left 
hand  one  the  electric  apparatus  called  the 


154 


CONTROLLERS   AND   SWITCHES.  155 

controller.  This  latter  apparatus  is  con- 
tained within  a  vertical  metal  case 
provided  on  its  upper  plate  with  notches, 
corresponding  to  different  speeds  of  the 
car.  By  this  apparatus  the  electric  cur- 
rent is  turned  on  and  off  and  the  power 
and  speed  of  the  motor  controlled. 


Different  systems  of  electric  traction 
employ  different  forms  of  controllers,  but 
all  operate  on  essentially  the  same  plan. 
It  will,  therefore,  suffice,  in  pointing  out 
the  method  in  which  the  controller 
operates,  to  limit  the  description  to  a  par- 
ticular form  in  common  use. 

4 

The  external  appearance  presented  by 
this  controller  will  be  seen  by  an  inspec- 
tion of  Fig.  70.  One  of  these  controllers 
is  mounted  on  the  front  platform  and  a 


156  ELECTRIC   STREET   RAILWAYS. 

similar  one  on  the  back  platform  of  the  car. 
It  is  operated  by  the  movement  of  the 
handle  H.  The  small  handle  A,  controls 
an  emergency  switch  used  for  reversing  the 
motion  of  the  car  when  necessary.  Coin- 
ing now  to  the  controller,  £>,  is  a  stop  to 
limit  the  range  of  motion  of  the  handle. 
In  the  position  shown  the  current  is  turned 
off,  and,  as  the  handle  is  turned  around 
in  a  clockwise  direction,  the  motors  are 
gradually  brought  into  action  with  increas- 
ing speed,  until,  when  the  projection  of  the 
handle  strikes  the  stop  $,  on  the  other 
side,  after  nearly  one  revolution,  the  maxi- 
mum speed  of  the  car  is  attained. 

In  order  to  open  the  controller,  a  sheet 
iron  door  is  provided,  closed  with  screw 
bolts,  which  can  be  manipulated  by  hand, 
the  hinges  of  these  bolts  being  shown 


CONTROLLERS   AND   SWITCHES.  157 


FlG.  70. — CONTROLLEK,  CLOSED. 


158  ELECTRIC    STREET   RAILWAYS. 

The  interior  construction  of  the  con- 
troller is  shown  in  Fig.  71.  The  lid  L  L, 
has  been  thrown  back  by  withdrawing  the 
bolts  at  the  hinges  j,  j.  By  further  with- 
drawing the  small  bolt,  e/J  shown  separately 
beneath  the  lid,  an  iron  cover  (7,  hinged 
on  the  core  <?,  of  the  electromagnet  M,  is 
also  thrown  back  from  the  cylinder  Y, 
leaving  it  exposed  to  view. 

The  switch  cylinder  is  turned  by  the 
movement  of  the  handle  If.  It  carries 
eleven  rings  of  insulating  material  rly  r,,  /•„ 
etc.,  upon  which  are  mounted  metallic  con- 
ducting segments  st,  sa,  ss,  of  different 
lengths  and  in  different  positions,  so  that, 
when  the  cylinder  is  turned,  they  come 
into  contact  at  different  times  with  the  row 
of  eleven  fixed  contact  springs  pt,  p*,  pa,  p*, 
etc.  It  is  these  contacts  which  effect  the 
changes  in  the  connections  for  producing  a 


CONTROLLERS    AND    SWITCHES.  159 


FIG.  71.— CONTROLLER,  OPEN. 


160  ELECTRIC    STREET   RAILWAYS. 

change  in  speed  of  the  car.  In  the  posi- 
tion shown,  while  the  handle  is  at  the  first 
notch  and  against  its  stop,  none  of  the 
segments  are  in  contact  with  their  springs, 
and  the  trolley  is  disconnected  from  the 
motors.  The  small  handle  h,  rotates  a 
small  cylinder  y,  carrying  eight  sets  of  me- 
tallic segments  and  having  a  row  of  eight 
fixed  metallic  contact  springs  qly  q^  q*.  By 
throwing  the  handle  A,  over  about  60°,  the 
segments  in  contact  with  the  springs  q, 
can  be  changed  and  also  the  direction  of 
the  current  through  the  armatures  of  the 
motors.  The  direction  of  rotation  of  the 
motor  can  thus  be  reversed,  backing  the 
car.  At  TFJ  is  a  star  wheel,  which  renders 
it  necessary  that  all  the  successive  contacts 
be  made  and  none  omitted  when  the 
handle  is  turned. 

After  contact  has  been  made  between 


CONTROLLERS   AND    SWITCHES.  161 

the  motors  and  the  trolley,  so  as  to  pass  the 
usual  current  strength  through  the  circuit ; 
then,  on  breaking  contact  either  at  the 
trolley,  or  at  the  ends  of  two  wires  in  the 
circuit  on  the  car,  a  spark  or  metallic  arc 
will  form,  which  may  be  from  two  inches 
to  five  inches  in  length.  This  is  the  char- 
acteristic arc  which  is  seen  when  the  trolley 
wheel  jumps  from  the  wire.  It  will  be 
readily  understood  that  the  formation  of 
arcs  of  this  character  within  the  con- 
troller, would  soon  cause  its  destruction. 
This  is  avoided  in  the  form  of  controller 
shown  in  the  figure  by  means  of  a  device 
called  the  magnetic  blow-out.  The  current 
through  the  motors  passes  through  a  coil 
wound  on  the  magnet  M,  around  the  iron 
core  c.  This  makes  the  core  <?,  a  powerful 
electromagnet,  and  its  projection,  or  pole- 
piece  CJ  becomes  a  large  magnetic  pole. 
AVhen  this  pole -piece  is  close  down  in  its 


162  ELECTRIC    STREET   RAILWAYS. 

normal  position  the  polar  ridges  P,  P,  P, 
rest  close  to  the  contact  strips  p^p^p*. 
While  the  motors  are  running,  the  magnet 
M,  being  excited,  produces  a  powerful 
magnetic  flux  surrounding  the  contact  sur- 
faces ph  p^  PS.  As  soon  as  any  break  in 
the  circuit  occurs  either  in  changing  con- 
nections during  running  of  the  motors,  or 
particularly  when  the  current  is  entirely 
shut  off,  the  severe  sparking,  which  would 
occur,  is  prevented  because  the  arcs  are 
blown  out  under  the  influence  of  the 
magnetic  flux  from  this  magnet.  In  other 
words,  an  arc  cannot  be  maintained  in  the 
presence  of  a  sufficiently  powerful  magnetic 
field. 

It  remains  now  to  explain  the  manner 
in  which  the  different  positions  of  the 
handle  H,  alter  the  speed  of  the  car. 
There  are  altogether  eleven  notches  or  sue- 


CONTROLLERS   AND   SWITCHES.  163 

cessive  positions  which  the  handle  IT,  and, 
consequently,  the  switch  cylinder,  can 
assume.  The  first  corresponds  as  already 
mentioned,  to  no  current,  as  in  Fig.  71. 
There  are  thus  left  ten  positions,  at  which 
the  speed  of  the  motor  can  be  varied. 

When  the  handle  is  pushed  to  the  first 
working  position,  the  segments  s^  s2j  s3, 
engage  with  their  corresponding  springs. 
The  effect  of  this  is  to  establish  the  con- 
nections shown  in  Fig.  72.  Hly  H%,  is  a 
resistance  made  up  of  a  coiled  insulated 
strip  of  iron.  Ml  and  M2,  are  the  motors. 
It  is  evident,  therefore,  that  the  current 
has  in  this  case  to  pass  successively  from 
the  trolley  T,  through  the  resistance 
j?!,  R%,  and  the  two  motors  to  the  ground 
6f.  The  resistance  H19  R%,  may  be  1  ohm, 
that  of  each  motor  armature  0.4  ohm,  and 
that  of  each  field  0.8  ohm.  The  total 


164  ELECTRIC   STREET   RAILWAYS. 

resistance    of    the    circuit    between    the 
trolley  and  the  track  is,  therefore,  3.4  ohms. 

If  we  assume  that  the  usual  pressure  is 
steadily  maintained   between   trolley  and 

T       ,Ri 


FIG.  72. — CONNECTIONS  CORRESPONDING  TO  FIRST  WORK- 
ING NOTCH  OF  CONTROLLER. 

track  at  500  volts,  then  the  maximum 
current  strength  which  may  pass  through 
the  car  circuit  under  these  conditions  is, 
by  Ohm's  law,  500  volts  divided  by  3.4 


CONTROLLERS   AND    SWITCHES.          165 

ohms  =  147  amperes.  Iii  practice  the 
current  never  rises  to  this  amount  for  two 
reasons;  namely, 

(1)  As  soon  as  the  circuit  is  closed,  the 
excitation  of  the   field   magnets  causes  a 
powerful  development  of  magnetic  flux  in 
the  motors,  which  momentarily  sets  up  a 
C.  E.  M.  F.  tending  to  check  or  oppose 
the   establishment   of    the   current.     This 
C.  E.  M.  F.  is  of  very  brief  duration,  say 
about  one  second,  so  that  if  the  motor  was 
prevented  from  running,  the  full  current 
strength  according   to   Ohm's  law  would 
soon    be    reached.     This    is    called    the 
C.  E.  M.  F.  of  self -induction }  because  it  is 
produced  by  the  magnetic  inductive  effect 
of  the  current  on  its  own  circuit. 

(2)  As  soon  as  current  passes  through 
the   motor   it   begins   to   turn  and   in  so 
doing   acts   as   a    dynamo    to   produce   a 
C.  E.  M.  F.  which  permanently  checks  the 


166  ELECTKIC    STREET   RAILWAYS. 

current,  and  the  faster  the  motor  runs  the 
greater  this  C.  E.  M.  F.  This  C.  R  M.  F. 
of  rotation  is  far  more  important  than  the 
C.  E.  M.  F.  developed  by  self-induction, 
since  it  always  operates  while  the  motors 
are  running,  whereas  the  C.  E.  M.  F.  of  self- 
induction  only  exists  during  changes  in 
current  strength. 

It  now  remains  to  be  explained  how  the 
C.  E.  M.  F.  of  rotation  automatically 
regulates  the  strength  of  current  and, 
therefore,  the  amount  of  electric  activity 
supplied  to  the  car.  Let  us  first  suppose 
that  the  motors  are  disconnected  from  the 
car  axles,  and  allowed  to  revolve  freely 
without  any  friction  whatever.  If  such  a 
state  of  things  were  possible,  the  torque, 
or  rotary  effort  of  the  armature  produced 
by  the  current  which  first  enters  them, 
would  soon  bring  the  armatures  to  a  high 


CONTROLLERS   AND   SWITCHES.      ,    167 

rate  of  speed,  under  which  circumstances 
the  C.  E.  M.  F.  generated  by  them  would 
be  so  great  that  very  little  current  would 
pass  through  them.  Thus,  if  the  total 
resistance  of  the  motor  circuit,  as  shown 
in  Fig.  72,  was  3.4  ohms,  and  the  amount 
of  power  required  to  drive  the  motors 
light  and  frictionless,  was  only  1  HP,  or 
say  750  watts,  this  would  mean  a  cur- 
rent strength  of  but  1.5  amperes,  since 
500  volts  x  1.5  amperes  =  750  watts. 
In  order  to  limit  the  current  strength  to 
1.5  amperes  in  a  circuit  of  3.4  ohms,  the 
effective  pressure  must  be  5.1  volts,  since 

5.1   VOltS  rpn  re      ,. 

=    1.5  amperes.     Ihe   effective 
3.4  ohms 

pressure  between  trolley  and  track  must, 
therefore,  under  these  circumstances,  be 
only  about  5  volts,  and  this  will  be  pro- 
duced by  such  a  speed  of  the  motor  as  to 
develop  a  C.  E.  M.  F.  of  495  volts;  for, 


168  ELECTRIC   STREET   RAILWAYS. 

since  500  volts  is  the  E.  M.  F.  supplied, 
and  495  is  the  C.  E.  M.  F.,  the  difference 
serving  to  drive  the  necessary  1.5  amperes 
through  the  resistance  of  the  circuit  will 
be  5  volts. 

If  now  some  small  frictional  resistance 
or  load  be  applied  to  the  motors;  or,  in 
other  words,  if  the  motors  be  required  to 
do  some  little  work,  the  activity  which 
they  will  require  to  be  supplied  with  to 
perform  this  work  may  amount  to  2  HP 
or,  approximately,  1,500  watts  (1.5  KW). 
Under  these  circumstances  the  current 
strength  must  increase  to  3  amperes,  since 
3  amperes  at  a  pressure  of  500  volts 
represents  the  needed  activity  of  1,500 
watts.  In  order  to  permit  3  amperes 
to  pass  through  the  resistance  of  the  cir- 
cuit (3.4  ohms)  the  effective  pressure 
must  be  10.2  volts,  since  10.2  volts  •*-  3.4 


CONTROLLERS   AND   SWITCHES.          169 

ohms  =  3  amperes.  The  E.  M.  F.  applied 
being  500  volts,  the  C.  E.  M.  F.  must  be 
490  volts  and  the  speed  of  the  motors  will 
drop  sufficiently  to  produce  only  490  volts 
C.  E.  M.  F.,  instead  of  495.  In  the  same 
way  if  we  suppose  the  motors  to  be 
coupled  to  their  respective  car  axles,  and 
work  to  be  required  from  them  to  drive 
the  car,  to  an  amount  of  say  10  HP, 
then  the  power  which  must  be  sup- 
plied to  the  motors  to  make  up  for  losses, 
both  frictional  losses  in  the  gears  and 
bearings,  and  electrical  losses  in  the  arma- 
ture and  field  coils,  may  be  15  HP,  or 
15  x  746  =  11,190  watts  =  11.19  KW. 
This  is  the  electric  activity  which  must  be 
supplied  from  the  circuit  to  the  motors, 
and  will  represent  a  current  strength  of 
22.38  amperes  at  a  pressure  of  500  volts. 
The  effective  pressure  required  to  drive 
22.38  amperes  through  a  resistance  of  3.4 


OF  THE 

UNIVERSITY 


170         ELECTRIC    STREET    RAILWAYS. 

ohms,  will  be  76.09  volts.  The  C.  E.  M.  F. 
required  to  limit  the  effective  pressure  to 
approximately  76  volts,  will  be  500  —  76 
=  424  volts,  and  the  motors  will  drop  in 
speed  until  this  is  the  C.  E.  M.  F.  which 
they  supply. 

Proceeding  in  this  way,  the  more  load 
we  put  on  the  motors ;  i.  e.,  the  more  we 
load  the  car,  or  the  steeper  the  grade  it  is 
necessary  to  ascend,  the  greater  the  electric 
activity  which  must  be  supplied  to  drive 
the  car,  and  the  greater  the  current 
strength  which  must  be  passed  through 
the  motors  to  produce  this  activity. 
Under  these  circumstances  the  motors  will 
continue  to  slacken  in  speed  so  as  to  per- 
mit the  current  to  pass,  and  will  always 
attain  such  a  speed  as  will  permit  the 
required  activity  to  enter  them  in  order  to 
perform  the  work  they  have  to  do.  When, 


CONTROLLERS   AND   SWITCHES.  171 

finally,  the  load  is  so  great  that  the  motors 
are  unable  to  run,  the  activity  received 
will  be  that  defined  by  Ohm's  law,  shortly 
after  the  circuit  is  closed.  In  this  limiting 
case,  all  the  activity  is  expended  as  heat  in 
the  resistance  Hly  R^  and  in  the  motors  M, 
M.  In  all  other  cases,  when  the  motors 
are  running,  some  of  the  activity  is  devel- 
oped as  heat,  but  by  far  the  greater  part  is 
developed  as  mechanical  activity  in  pro- 
pelling the  car. 

On  the  other  hand  a  reduction  in  the 
load  of  the  motors  must  be  followed  by  an 
increase  in  their  speed.  This  increase,  how- 
ever, will  be  arrested  as  soon  as  the  C.  E.  M. 
F.  is  increased  to  the  value  which  limits  the 
current  strength  to  that  required  for  the  rate 
at  which  work  is  being  mechanically  done. 

In  all  cases  it  will  be  evident  that  the  E. 


172          ELECTRIC   STREET   RAILWAYS. 

M.  F.  existing  between  the  trolley  and  the 
track,  which  we  have  assumed  to  be 
maintained  at  500  volts,  is  to  be  met  by 
an  equal  total  C.  E.  M.  F.  in  the  car  circuit 
T,  G.  If  the  motors  are  at  rest,  this  C.  E. 
M.  F.  must  be  entirely  due  to  drop  in  the 
resistance,  represented  by  the  product  of 
the  current  strength  in  amperes  and  the 
resistance  in  ohms.  For  example,  with  the 
car  held  at  rest,  we  know  that  the  current 
will  be  147  amperes  in  the  case  of  Fig.  72, 
and  this  multiplied  by  the  total  resistance 
of  3.4  ohms,  represents  a  drop  of  pressure 
amounting  to  500  volts. 

When,  however,  the  motors  are  running, 
their  C.  E.  M.  F.  of  rotation  will  necessi- 
tate a  smaller  drop  in  the  resistance  of 
their  circuit.  Thus,  if  the  motors  are  pro- 
ducing together  a  C.  E.  M.  F.  of  400  volts, 
then  the  drop  in  the  resistance  Hly  7?2,  will 


CONTROLLERS   AND   SWITCHES.          173 

be  only  100  volts,  and  if  the  motors  pro- 
duced together  a  C.  E.  M.  F.  of  rotation  of 
490  volts,  the  drop  will  be  reduced  to  10 
volts.  The  activity  available  for  mechani- 
cal work  is  the  product  of  the  C.  E.  M.  F. 
of  rotation  and  the  current  strength.  For 
example,  if  the  motors  in  Fig.  72  develop  to- 
gether a  C.  E.  M.  F.  of  rotation  amounting 
to  490  volts,  and  the  drop  in  the  resistance 
of  motors  and  rheostat  is,  therefore,  10 
volts,  the  current  strength,  which  will  pro- 
duce this  drop,  will  be  by  Ohm's  law 

10    volts  •      ,  -, 
—       —  2.94  amperes,  approximately. 

The  total  activity  taken  from  the  circuit 
between  T  and  6r,  will,  therefore,  be  500 
volts  X  2.94  amperes  =  1,470  watts.  Of 
this,  the  amount  capable  of  producing  me- 
chanical activity  is  490  volts  X  2.94  amperes 
=  1,440  watts,  while  that  only  capable  of 
producing  heat  is  10  volts  x  2.94  amperes 


174  ELECTRIC   STREET   RAILWAYS. 

=  29.4  watts.  It  is  evident  that  the 
greater  the  proportion  of  C.  E.  M.  F.  of 
rotation  to  the  drop  in  the  circuit  T,  G, 
for  any  given  current  the  greater  will  be 
the  activity  used  for  propelling  the  car. 

We  will  now  explain  the  use  of  the  resist- 
ance R^,  H2.  In  the  first  place  if  the  resist- 
ance jffj,  J?2,  be  removed  from  the  circuit  in 
Fig.  72,  the  total  resistance  between  T,  and 
6r,  will  be  reduced  to  2.4  ohms,  and  the 
possible  current  strength  by  Ohm's  law, 
such  as  would  exist  when  the  car  was 
absolutely  prevented  from  moving,  would 

500  volts 

be  —    208     amperes,    approxi- 

2.4  ohms 

mately.  In  other  words,  a  current  of  208 
amperes  would  maintain  a  drop  of  500 
volts  in  a  total  resistance  of  2.4  ohms. 
The  first  rush  of  current  would,  therefore, 
be  greater,  and  the  current  strength  dur- 


CONTROLLERS    AND   SWITCHES.          175 

ing  the  time  when  the  motors  were  acceler- 
ating and  reaching  their  limiting  speed  of 
rotation  would  be  greater,  so  that  the  car, 
would  start  from  rest  with  a  greater  jerk, 
and,  moreover,  waste  a  greater  amount  of 
power  in  the  process.  The  greater  the 
amount  of  resistance  which  is  introduced 
into  the  circuit  of  the  motors  at  the  start, 
the  smaller  the  current  which  will  pass 
through  them,  the  more  quietly  the  car  will 
start  and  reach  the  speed  which  limits  the 
C.  E.  M.  F.  of  rotation,  and  the  less  the 
activity  which  will  be  wasted  during  that 
period  in  which  the  motors  are  accelerating 
up  to  this  speed. 

On  the  other  hand,  the  continued  use  of 
a  resistance  Hly  Hz  is  more  or  less  wasteful 
after  the  car  has  been  brought  up  to  speed, 
because  it  produces  a  drop  in  the  circuit 
and  prevents  the  C.  E.  M.  F.  of  rotation 


176  ELECTRIC    STREET   RAILWAYS. 

from  coming  into  full  play.  For  example, 
if  the  current  which  the  circuit  must  re- 
ceive under  given  conditions  of  load  is  50 
amperes,  the  drop  in  the  resistance  of  1 
ohm  at  Hi,  Hz,  will  be  50  amperes  X  1 
ohm  =  50  volts,  and  the  effect  is  tempor- 
arily the  same  as  though  the  motors  J/j, 
M&  were  connected  to  the  trolley  circuit 
between  T  and  G,  without  a  resistance, 
but  with  450  volts  pressure.  The  activity 
expended  in  the  motors,  both  as  drop  in 
their  resistance,  and  as  available  energy 
against  their  C.  E.  M.  F.  of  rotation,  will 
be  450  volts  x  50  amperes  =  22,500  watts. 
The  circuit  between  T&nd  ff,  supplies  a 
total  activity  of  500  volts  X  50  amperes  = 
25,000  watts. 

The  effect,  therefore,  of  constantly  main- 
taining the  resistance  Hl9  JR2j  in  the  circuit 
of  Fig.  72,  is  to  expend  activity  in  it  as 


CONTROLLERS    AND   SWITCHES.  177 

heat,  and  thus  prevent  the  motors  from 
reaching  as  high  a  speed  as  they  otherwise 
would,  while,  of  course,  it  is  an  advantage 
to  be  able  to  run  slowly,  it  is  nevertheless 


FIG.  73.— STREET  CAR  RESISTANCE  COIL. 

a  disadvantage  to  waste  power  in  the  re- 
sistance for  this  purpose.  The  use  of  a 
certain  amount  of  resistance  is,  therefore, 
beneficial  during  periods  of  starting,  and 
where  the  advantage  of  running  at  low 
speeds  offsets  the  disadvantage  of  wasting 
power. 


178  ELECTRIC    STREET    RAILWAYS. 

The  resistance  R^  H2,  is  commonly  made 
in  the  form  shown  in  Fig.  73.  Here  the 
coils  are  placed  in  an  iron  box  of  such 
dimensions  as  to  permit  it  to  be  attached 
by  screws  or  bolts  at  the  lower  part  of  the 
car  body.  It  is  purposely  left  open  to  per- 
mit the  circulation  of  air  and  thus  carry  off 
the  heat  generated  in  the  coils. 

Let  us  now  inquire  what  happens  when 
the  controller  is  turned  to  the  next  or  sec- 
ond working  notch.  The  effect  of  this  is 
shown  diagrammatically  in  Fig.  74.  An 
inspection  of  the  figure  will  show  that  half 
the  extra  resistance  is  cut  out  of  circuit ; 
namely,  Rv.  This  has  the  effect  of  reducing 
the  drop  of  pressure  in  the  resistance  for  a 
given  current  strength  passing  through  the 
circuit.  Consequently,  the  motors  have  to 
ran  faster  to  make  up  the  total  C.  E.  M.  F. 
of  500  volts,  so  that  the  speed  of  the  car  is 


CONTROLLERS   AND    SWITCHES. 


179 


increased.  For  example,  if  in  the  case  of 
Fig.  72,  a  drop  of  100  volts  occurs  in  the 
resistance  j?b  J22,  requiring  400  volts  to  be 


FIG.  74. — CONNECTIONS  CORRESPONDING  TO  SECOND 
WORKING  NOTCH  OF  CONTROLLER. 

made  up  by  the  motors  in  C.  E.  M.  F.  of 
rotation  and  drop  in  their  resistances,  then, 
when  the  resistance  Hiy  is  cut  out,  as  in  Fig. 


180  ELECTRIC    STREET   RAILWAYS. 

74,  with  the  same  current  strength  there 
will  be  only  50  volts  drop  in  that  half  of 
resistance  R%,  remaining  in  the  circuit,  and 
450  volts  must  be  made  up  by  the  two 
motors  in  C/  E.  M.  F.  of  rotation  and 
drop  ;  they  will,  therefore,  increase  in  speed 
to  this  extent.  Consequently,  the  effect  of 
cutting  out  resistance  from  the  circuit  is  to 
cause  the  car  to  increase  in  speed  to  an  ex- 
tent which  will  depend  entirely  upon  the 
amount  of  drop  reduced,  which  in  its  turn 
will  depend  upon  the  load  of  the  car.  If 
the  car  is  very  light,  and  is  steadily  running 
on  a  level  portion  of  the  track,  the  drop  in 
the  resistance  will  be  very  small  and  the 
effect  of  halving  this  drop  will  be  very 
small,  so  that  the  car  will  receive  very  lit- 
tle increase  in  its  steady  speed  by  moving 
to  the  second  notch.  If,  on  the  contrary, 
the  motor  is  heavily  loaded,  or  is  running 
up  a  steep  grade,  there  will  be  a  heavy 


CONTROLLERS    AND    SWITCHES.  181 

drop  in  the  resistance  JRly  J?2,  especially  on 
starting,  due  to  the  stronger  current  and 
greater  activity  required,  so  that  cutting 
out  half  the  resistance  and  drop  will  pro- 
duce a  greater  increase  in  speed. 

Fig.  75,  shows  the  effect  of  turning  the 
controller  handle  to  the  third  notch.  Here, 
as  will  be  seen,  all  the  resistance  Hly  R^  is 
cut  out,  so  that  the  motors  have  to  make 
up  in  drop  and  C.  E.  M.  F.  of  rotation,  the 
full  line  E.  M.  F.  existing  between  trolley 
and  ground.  They  will,  therefore,  require, 
other  things  remaining  the  same,  to  main- 
tain a  higher  speed  than  in  either  of  the 
preceding  positions  of  Figs.  72  and  74. 
The  total  resistance  of  their  circuit  between 
jTand  6?,  is  2.4  ohms. 

Turning  the  controller  handle  to  the 
next,  or  fourth  working  notch,  the  effect 


182 


ELECTRIC    STREET   RAILWAYS. 


produced  is  represented  diagrainmatically 
in  Fig.  76.  Here,  as  in  Fig.  75,  the  extra 
resistance  is  entirely  cut  out  and  in  addition 


FIG.  75. — CONNECTIONS  CORRESPONDING  TO  THIRD 
WORKING  NOTCH  OP  CONTROLLER. 

the  field  magnet  coils  of  each  motor  are 
provided  with  a  by-path  or  shunt  $i,  S%,  so 
that  the  current  through  the  circuit  divides 


CONTROLLERS   AND    SWITCHES. 


183 


at   each   field   magnet,   a  part  only  going 
through  the  magnets,   and  the  remainder 
going  around  through  the  shunt,  all  of  the 
T 


FIG.  76. — CONNECTIONS  CORRESPONDING  TO  FOURTH 
WORKING  NOTCH  OP  CONTROLLER. 

current,    however,    passing    through    each 
armature. 

The  effect  of  shunting  the  field  magne- 
tizing coils  is  to  weaken  them  ;  i.  #.,  haa 


tTHlVEBSlTT 


184  ELECTKIC    STREET   RAILWAYS. 

f 

the  same  effect  as  taking  wire  off  the  coil, 
or  of  reducing  the  equivalent  current 
strength.  The  magnetism  produced  by 
the  field  magnets  of  the  motors,  will, 
therefore,  be  reduced,  and  in  order  to 
make  up  a  given  C.  E.  M.  F.,  with  this 
reduced  magnetism,  a  greater  speed  must 
be  attained  by  the  armatures.  The  car 
has,  therefore,  to  run  faster  owing  to  the 
introduction  of  the  shunts.  At  the  same 
time,  if  the  grade  and  load  remain  the 
same  the  greater  speed  of  the  car  will  call 
for  a  greater  expenditure  of  mechanical 
power,  and,  consequently,  a  greater  ex- 
penditure of  electric  current  and  activity, 
so  that,  since  each  motor  is  called  upon  to 
produce  a  total  C.  E.  M.  F.  of  250  volts 
in  drop  and  in  rotation,  this  C.  E.  M.  F. 
will  be  developed  by  a  greater  speed  in 
the  weakened  magnetic  fields,  but  with  a 
greater  current  supply  and  to  that  extent 


CONTROLLERS   AND   SWITCHES.  185 

a  greater  drop ;  for,  if  the  current  strength 
supplied  was  insufficient  to  maintain  the 
increased  activity  of  the  car,  then  a  de- 
crease in  speed  would  occur  until  the  cur- 
rent supply  was  made  up. 

The  connections  corresponding  to  the 
fifth  working  notch  are  the  same  as  those 
shown  in  Fig.  74,  that  is  to  say,  the  re- 
sistance 7?2,  is  first  restored  to  the  circuit 
before  changing  the  connections  at  the 
next  step. 

The  condition  of  affairs  when  the  con- 
troller is  turned  to  the  sixth  working 
notch  is  represented  in  Fig.  77.  Here,  it 
will  be  observed  that  the  shunts  around 
the  field  magnets  are  withdrawn,  and  the 
resistance  R^  is  restored  to  the  circuit, 
while  the  second  motor  M&  is  completely 
cut  out.  The  first  motor  J/  has  now  to 


186 


ELECTRIC   STREET    RAILWAYS. 


make  up  the  full'  pressure  of  the  line  with 
the  aid  of  the  drop  in  half  the  resistance. 
Excluding  the  drop  in  the  resistance 


FIG.  77. — CONNECTIONS  CORRESPONDING  TO  SIXTH 
WORKING  NOTCH  OP  CONTROLLER. 

the  speed  will  be  roughly  double  that 
corresponding  to  the  connections  in  Fig. 
75 ;  for,  the  single  motor  armature  must 
produce,  roughly,  double  the  C.  E.  M.  F. 


CONTROLLERS    AND   SWITCHES.  187 

of  rotation  that  it  produces  when  it  was 
aided  by  the  motor  M2. 

The  connections  of  the  seventh  working 
notch  are  the  same  as  for  the  sixth,  or  re- 
main as  shown  in  Fig.  77.  This  is  merely 
for  the  purpose  of  not  making  the  next 
change  too  suddenly,  requiring  the  motor- 
man  to  take  a  certain  time  in  turning  his 
handle  for  two  notches,  so  as  to  avoid 
abrupt  changes  in  speed. 

The  conditions  produced  when  the 
eighth  working  notch  is  reached  are 
indicated  diagrammatically  in  Fig.  78. 
Here  the  second  motor  M2,  which  was 
withdrawn  from  the  circuit  in  Fig.  77,  is 
replaced  in  parallel  with  J/i,  instead  of  in 
series ;  that  is  to  say,  the  current  through 
the  circuit  divides,  half  passing  through 
MI,  and  half  through  M2.  Each  motor, 


188 


ELECTRIC    STREET    RAILWAYS. 


however,  must  make  up,  disregarding  drop 
'in  J?2,  the  full  pressure  of  500  volts  be- 
tween trolley  and  track,  and  the  speed  of 
rotation  would  remain  practically  un- 


FIG.  78.— CONNECTIONS  CORRESPONDING  TO  EIGHTH 
WORKING  NOTCH  OF  CONTROLLER. 

changed,  except  that  the  current,  being 
approximately  halved  through  each  mag- 
net, the  strength  of  the  magnetic  field  is 
weakened,  and  the  armatures  have  to  run 


CONTROLLERS   AND    SWITCHES. 


189 


faster  to  make  up  the  required  C.  E.  M.  F., 
in  this  weakened  magnetism.  The  speed 
of  the  car  will,  therefore,  be  greater  than 
in  the  case  represented  in  Fig.  77. 


FIG.  79. — CONNECTIONS  CORRESPONDING  TO  NINTH 
WORKING  NOTCH  OF  CONTROLLER. 

The  effect  of  turning  the  controller 
handle  to  the  ninth  working  notch  is  repre- 
sented in  Fig.  79.  Here  the  resistance  J?2, 
is  completely  cut  out  of  circuit  and  the 
two  motors  are  in  parallel  as  in  the  last 


190 


ELECTRIC    STREET    RAILWAYS. 


case ;  or,  as  it  is  sometimes  called,  are  con- 
nected in  multiple.  The  speed  will  be 
increased,  owing  to  the  fact  that  the  drop 
previously  existing  in  J?2,  now  requires  to 
be  made  up  by  the  motors  alone. 


AAAAAAPAAAAAA 


FIG.  80. — CONNECTIONS  CORRESPONDING  TO  TENTH 
WORKING  NOTCH  OF  CONTROLLER. 

Fig.   80,  represents  the  connections  cor- 
responding to  the  tenth  and  last  working 


CONTROLLERS   AND   SWITCHES.  191 

notch  ;  i.  e.,  the  connections  for  full  speed. 
Here  the  only  change  from  the  connec- 
tions of  Fig.  79  lies  in  the  restoration  of 
the  shunts  around  the  field  magnets,  thereby 
reducing  their  excitation  and  requiring 
an  increased  armature  speed  in  order  to 
maintain  the  C.  E.  M.  F.  Each  motor,  as 
before,  has  to  produce,  in  C.  E.  M.  F.  and 
drop,  the  full  pressure  of  500  volts,  and 
when  the  field  is  weakened,  the  speed  for 
a  given  C.  E.  M.  F.  of  rotation  has  to 
increase. 

It  will  be  observed,  therefore,  that  the 
movement  of  the  controller  handle  through 
the  successive  notches,  results  in  an  in- 
creasing speed  of  the  car.  Of  course 
movement  in  the  opposite  direction  results 
in  changing  the  connections  in  opposite 
order  of  succession ;  and,  consequently, 
slows  the  car. 


192  ELECTRIC    STREET   RAILWAYS. 

There  is  no  definite  or  precise  speed 
which  corresponds  to  each  notch,  since  that 
will  depend  upon  the  load  of  the  car  and 
the  gradient  at  which  it  runs.  In  other 
words,  it  will  depend  upon  the  activity 
which  the  motors  exert.  The  lighter  the 
load  -for  any  given  notch  or  set  of  connec- 
tions, the  faster  the  motors  will  run.  On 
the  contrary,  an  increase  of  load  at  any 
time,  even  without  touching  the  controller 
handle,  will  result  in  a  diminution  of 
speed. 

The  function  of  the  small  handle  A,  is  to 
reverse  the  direction  of  current  through  the 
two  motor  armatures,  and,  consequently, 
to  reverse  their  direction  of  rotation. 
As  this  cannot  be  safely  accomplished 
during  the  running  of  the  motors,  the 
handle  A,  is  so  arranged  mechanically  that  it 
cannot  be  turned  until  the  controller  handle 


CONTROLLERS    AND    SWITCHES.  193 

H,  is  at  the  "  off  position "  on  the  first 
notch  ;  so  that  before  the  car  can  be  reversed 
the  current  must  first  be  shut  off.  This 
prevents  any  arcing  on  the  contacts  of  the 
reversing  cylinder  y.  All  the  arcs  wnich 
tend  to  form  on  the  contact  segments  of 
the  large  cylinder  are  extinguished  by  the 
action  of  the  magnet  M,  which  is  always 
in  the  circuit. 

At  the  bottom  of  the  controller  are  two 
switches  m  and  n,  respectively.  These 
are  commonly  employed  to  cut  out  one  of 
the  motors  on  the  car,  if  by  any  accident 
it  should  become  disabled.  For  example, 
if  the  brushes  of  motor  M±,  should  fail  to 
make  good  contact,  or  give  other  electrical 
trouble,  that  motor  can  be  entirely  cut  out 
of  circuit.  Similarly,  by  lifting  the  switch 
handle  n,  the  motor  M^  can  be  entirely  cut 
out  of  circuit.  In  such  a  case  the  car  is 


194  ELECTRIC    STREET   RAILWAYS. 

operated  by  the  remaining  motor,  and 
only  such  notches  can  be  used  with  the 
controller  handle  as  will  be  available  for 
the  operation  of  that  motor. 


H 


FIG.  81. — STREET  CAR  CONTROLLER. 

Another   form   of   controller   is   shown 
in  Figs.  81  and  82,     Here,  as  before,  we 


CONTROLLERS   AND   SWITCHES. 


195 


have  the  main  controller  handle  If,  and  a 
small  reversing  handle  k.  The  method  of 
operation  is  substantially  the  same  in 


FIG.  82.— CONTROLLER  OF  FIG.  81  OPENED  FOB 
INSPECTION. 

all  controllers.  In  this  case,  however, 
no  attempt  is  made  to  blow  out  the  arcs 
magnetically  when  breaking  the  circuit. 
Instead  of  this  the  arc  is  caused  to  occur 


196  ELECTRIC    STREET    RAILWAYS. 

simultaneously  at  a  number  of  segments  in 
series,  so  as  to  produce  a  number  of  small 
arcs  instead  of  a  single  large  one.  This 
greatly  reduces  the  heat  and  deflagrating 


FiG."83. — FORM  OF  CONTROLLER  RESISTANCE. 

power  of  the  arcs.  The  contact  points 
at  which  they  occur  are  renewed  from 
time  to  time. 

Fig.    83,    shows    a   form   of    resistance 
employed  with  the  controller  represented 


CONTROLLERS    AND    SWITCHES.  197 

in  Figs.  81  and  82.  Here  the  resistances 
are  formed  of  strips  of  sheet  iron,  wound 
upon  insulating  frames,  in  coils  or 
cylinders,  three  of  which  are  stowed  in  the 
iron  box  shown,  in  such  a  manner  as  to 
allow  free  circulation  of  air  to  carry  off 
the  heat  that  may  be  generated  in  them. 
There  are  four  screw  terminals  tiy  t2,  t&  £4, 
placed  on  an  insulating  slab  at  the  top 
of  the  case  for  the  wires  to  connect  with. 

The  controller  of  a  car  may  be  regarded 
as  a  complex  switch  capable  of  effecting 
the  different  connections  such  as  we  have 
indicated.  Usually  there  is  one  controller 
at  each  end  of  the  car.  The  handle  H, 
is  carried  from  one  controller  to  the  other 
according  to  the  direction  in  which  the  car 
is  to  be  run. 

In  order   to    protect    the    controller  or 


198  ELECTRIC    STREET   RAILWAYS. 

motors  from  any  excess  of  current,  an 
automatic  cut-out  or  safety  fuse  is  employed 
in  the  circuit.  This  consists  of  a  copper 
wire,  of  such  size  that  it  will  melt  when 
the  current  attains  an  excessive  strength. 


FIG.  84.— FUSE  BLOCK. 

The  wire  is  enclosed  in  a  box  or  block 
called  a  fuse  block,  placed  in  a  suitable 
position  on  the  car,  usually  on  the  plat- 
form overhead,  where  it  can  be  readily 
inspected.  A  form  of  fuse  block  is  repre- 
sented in  Fig.  84.  The  block,  as  it 


CONTROLLERS   AND   SWITCHES.          199 

appears  when  closed,  is  shown  at  C,  and,  as 
it  appears  open,  at  0.  A  block  of  hard 
wood  j5,  carries,  secured  to  its  edge,  two 
screw  binding  posts  Sl  and  S&  and  tongues 
Tly  T2.  The  clips  are  permanently  in  con- 
nection wTith  the  trolley  on  one  side,  and 
the  controller  on  the  other,  so  that  the 
current  has  to  pass  from  the  trolley 
through  the  fuse  block  by  means  of  these 
clips.  Connection  is  made  between  the 
clips  through  a  wire,  usually  either  No. 
12,  or  No.  14,  A.  W.  Gr.,  running  around 
the  edge  of  the  block  B,  and  having  its 
extremities  clamped  under  the  screws  ^ 
and  Sg.  The  lid  Z,  of  the  box,  as  well  as 
its  interior,  are  lined  with  asbestos  cloth  to 
prevent  damage  through  the  melting  of 
the  copper  fuse, 

In  addition    to  the  controller  and  fuse 
block   there    is    usually   added  a  canopy 


200  ELECTRIC    STREET    RAILWAYS. 

switch  at  each  end  of  the  car.  This  switch 
is  provided  for  the  purpose  of  permitting 
the  motorman  to  turn  the  current  on  or  off 
the  car  as  desired,  when,  for  example,  he 
wishes  to  inspect  a  fuse  block  or  con- 
troller, without  pulling  down  the  trolley 


FIG.  85. — CANOPY  SWITCH. 

pole.  It  receives  its  name  of  canopy 
switch  from  its  position  beneath  the 
canopy  or  roof  of  the  platform. 

Fig.  85,  shows  a  form  of  canopy  switch. 
A  cast  iron  box  B,  encloses  the  working 


COMTROLLERS   AND    SWITCHES.  201 

parts  and  screws  up  against  the  canopy. 
The  handle  H,  projects  from  this  box  and 
can  be  moved  sideways  in  the  slot  or  groove 
provided  for  the  purpose.  This  insulat- 
ing handle  is  fastened  to  a  metallic  blade 
which  closes  a  contact  with  a  clip  C,  thus 
establishing  the  main  circuit  from  the 
trolley  to  the  controller.  S,  S,  are  two 
slotted  slabs  between  which  the  handle 
plays. 

To  protect  the  motors  and  apparatus  on 
a  street  car  from  electrical  discharges  pro- 
duced by  atmospheric  disturbances  ;  i.  e., 
from  lightning  discharges,  a  lightning 
arrestor  is' usually  included  in  their  equip- 
ment. A  form  of  lightning  arrestor  is 
represented  in  the  accompanying  figure  86. 
Here  a  cast  iron  box  B,  B,  with  its  lid 
L,  L,  removed  for  inspection  of  its  inte- 
rior, has  a  pair  of  marble  slabs,  the  upper 


202 


ELECTRIC   STREET    RAILWAYS. 


one  of  which  is  shown  at  Jt/J  clamped 
together  by  screws.  A  groove  runs  down 
their  interior  surface,  between  two  inetal- 


FIG.  86. — LIGHTNING  AKRESTOR. 

lie  pieces  cl  and  0a,  in  electrical  connection 
with  the  leads  or  insulated  conducting 
wires  Clt  Cv  This  groove  is  black-leaded 


CONTROLLERS  AND   SWITCHES.          203 

in  such  a  manner  as  to  provide  a  ready 
path  for  discharges  of  very  high  E.  M.  R, 
such  as  those  which  accompany  lightning 
discharges,  but  forms  an  effectual  barrier, 
or  high  resistance  path,  to  currents  from  a 
pressure  of  500  volts.  Should  a  lightning 
discharge  occur  between  the  trolley  wire 
<7n  and  the  ground  or  track  wire  <72,  the 
dynamo  current  will  be  unable  to  follow 
this  discharge  owing  to  the  rapidity  with 
which  the  heated  column  parts  with  its 
heat  to  the  marble  blocks.  In  other 
words,  the  conducting  path  is  chilled  so 
suddenly,  after  the  passage  of  the  momen- 
tary high-pressure  discharge,  that  the 
dynamo  current  is  unable  to  follow.  If 
this  were  not  effected  the  high-pressure 
discharge  would  establish  a  very  powerful 
and  dangerous  arc  between  trolley  and 
track. 


CHAPTEE  VIII. 

TEOLLEYS. 

THE  existing  system  of  trolleys  and 
trolley  wires  for  street  railway  cars,  simple 
as  it  seems,  has,  nevertheless,  been  the  out- 
come of  no  little  practical  development 
and  experience.  At  the  present  time  the 
system  in  almost  universal  use  is  the 
single-trolley  system.  In  this  system,  a 
current  is  taken  from  an  overhead  wire 
suspended  over  the  street.  After  passing 
through  the  motors  the  current  returns  to 
the  power  station,  through  the  track  and 
ground  return. 

The   well  known   mechanism   provided 

204 


TROLLEYS.  205 

for  transferring  the  current  from  the  trol- 
ley wire  to  the  cars,  called  the  trolley  mech- 
anism, is  shown  in  Fig.  87.  As  will  be 
seen,  it  consists  of  a  light  steel  pole  p, 
called  the  trolley  pole,  mounted  on  a  base 
b,  called  the  trolley  base,  and  provided  at 
its  extremity  with  a  light  wheel  t,  called 
the  trolley  wheel.  The  rope  r,  called  the 
trolley  rope,  is  provided  for  pulling  the 
trolley  away  from  the  trolley  wire  w  w, 
and  for  aiding  in  replacing  it. 

Simple  as  the  trolley  mechanism  appears, 
nevertheless,  certain  conditions  must  be 
satisfied,  in  order  to  ensure  efficient  opera- 
tion. One  of  the  most  important  of  these 
is  that  sufficiently  firm  pressure  or  con- 
tact be  steadily  maintained  between  the 
trolley  and  the  wire  under  which  it  runs. 
Moreover,  this  contact  must  be  flexible. 
The  requisite  flexibility  is  obtained  both 


206  ELECTRIC    STREET   RAILWAYS. 


FIG.  87. — PASSENGER  CAR  WITH  TROLLEY. 


TROLLEYS.  207 

by  the  flexibility  of  the  trolley  wire  itself, 
and  the  mounting  or  support  of  the  trolley 
on  its  base.  Means  too,  are  provided  for 
reversing  the  direction  of  the  trolley  pole, 
so  that  the  car  may  be  driven  in  either 
direction.  For  obvious  mechanical  reasons 
the  trolley  pole  always  slants  away  from 
the  direction  in  which  the  car  moves. 

The  trolley  wheel,  or  trolley,  is  the  name 
given  to  the  revolving  part  which  is  sup- 
ported at  the  top  of  the  trolley  pole,  and 
maintained  in  rolling  friction  upon  the 
under  side  of  the  trolley  wire.  Its  func- 
tion is  to  maintain  electric  contact  with 
the  wire,  so  as  to  take  from  it  the  current 
required  for  the  operation  of  the  car. 
One  form  of  trolley  wheel  is  seen  in  Fig. 
88.  As  here  shown,  it  consists  of  a  light 
wheel  TFJ  usually  of  gun  metal,  sup- 
ported in  a  frame  or  harp  II,  and  running 


208 


ELECTRIC  STREET  RAILWAYS. 


freely  upon  a  spindle,  not  shown  in  the  fig- 
ure, passing  through  both  harp  and  wheel. 
The  grooved  form  given  to  the  wheel  not 
only  serves  the  purpose  of  ensuring  a 


FIG.  88. — TROLLEY  WHEEL  AND  HARP. 

more  extended  rolling  contact  surface 
with  the  wire,  but  also  serves  to  prevent 
the  trolley  from  slipping  off  the  wire.  The 
spring  w,  pressing  against  the  face  of  the 
trolley,  maintains  good  electric  contact 
between  the  wheel  and  an  insulated  wire 


TROLLEYS. 


209 


which    passes   down    through  the  trolley 
pole  to  the  car. 


FIG.  89.— FORM  OF  TROLLEY  WHEEL. 

Various    forms  of   trolley  wheels  have 
been    devised.     It  is  essential   that   they 


FIG.  90.— FORM  OP  TROLLEY  WHEEL. 


210          ELECTRIC    STREET   RAILWAYS. 

shall  be  as  light,  rigid  and  freely  running 
as  possible.  For  this  purpose,  special 
attention  is  paid  to  their  lubrication, 
which  is  usually  effected  by  employing  a 
bushing  of  graphite,  or  other  lubricating 
material. 


FIG.  91. — SECTION  OP  TIIOLLEY  WHEEL,  SHOWING 
LUBRICATING  BUSHING. 


As  an  illustration  of  some  of  the  various 
forms  of  trolley  wheels  those  shown  in  Figs. 
89  and  90  may  be  taken.  It  will  be  ob- 
served that  these  wheels  are  ribbed,  so  as 
to  ensure  strength  combined  with  light- 


TROLLEYS.  211 

ness.  Moreover,  should  the  rim  of  the 
wheel  wear  out  and  drop  off  dining  a 
trip,  the  trolley  wire  will  still  be 
gripped  by  the  ribs  It,  H.  The  bushing 
of  lubricating  material  is  seen  at  b,  Fig.  91, 
which  shows  a  section  through  the  wheel  of 


FIG.  92.— LUBRICATING  BUSHING. 

Fig.  89.  Here  the  lubricating  bushing  B, 
is  seen  in  place  at  the  centre  of  the  hollow 
wheel.  Fig.  92  shows  a  form  of  bushing 
ready  for  insertion. 

At  times  during  winter,  when  the 
trolley  wire  is  covered  with  sleet,  some 
difficulty  is  experienced  in  taking  off  the 


212  ELECTRIC   STREET   RAILWAYS. 

current,  ice  being  practically  an  insulator. 
Various  devices  have  been  suggested  to 
avoid  this  difficulty.  A  form  of  trolley 
wheel,  which  assists  in  clearing  sleet  from 

o 

the  wire,  and  allows  the  fragments  of  ice 


FIG.  93.— SLEET-CUTTING  TROLLEY  WHEEL. 

to  escape  through  the  sides  of  the  wheel 
is  shown  in  Fig.  93. 

The  trolley  pole  is  in  almost  all  cases  a 
steel  tube,  tapering  toward  the  top.  Its 
lower  end  is  mounted  on  the  trolley 
frame  or  base.  Springs  are  connected 


TROLLEYS. 


213 


between  the  base  aiid  the  pole  in  such  a 
manner  as  to  maintain  the  pole  in  contact 
with  the  wire,  with  a  nearly  uniform  pres- 
sure, under  all  conditions  of  dip  or  devi- 
ation of  the  trolley  wire.  Various  trolley 


FIG.  94. — TROLLEY  BASE. 

poles  and  bases  have  been  employed.  A 
well  known  form  of  trolley  base  is 
shown  in  Fig.  94.  Here  the  pole  P, 
terminates  in  a  fork  attached  to  a  pair 
of  sectors  8,  8,  forming  a  frame,  capable 
of  revolving  about  a  vertical  axis  V, 


214  ELECTRIC   STREET   RAILWAYS. 

so  as  to  accommodate  the  pole  and  trol- 
ley wheel  to  turns  or  curves  in  the 
track  and  trolley  wire.  The  six  spiral 
springs  6f,  maintain  a  tension  upon  these 
sectors  tending  to  force  the  pole  f, 
upwards.  This  tension  can  be  altered  by 
the  screw  adjustment  behind  the  springs. 
In  order  to  be  able  to  use  the  trolley 
when  the  direction  of  the  car  is  reversed, 
the  pole  is  first  pulled  down  from  the 
trolley  wire  and  then  swung  around  the 
vertical  pivot  V,  when  it  is  allowed  to 
re-engage  with  the  wire  in  the  opposite 
direction. 

Another  frame  and  pole  called  the 
Boston  trolley  apparatus  is  represented  in 
Fig.  95.  The  wooden  frame  F F F F, 
is  screwed  to  the  roof  of  the  car.  It 
carries  a  spindle.,  working  on  a  horizontal 
axis  and  bearing  the  pole  jP,  at  its  centre. 


TROLLEYS. 


215 


Eight  spiral  springs  G,  G,  maintain  the 
requisite  tension  upon  the  pole  under 
the  screw  adjustment  s  s.  Two  smaller 
spiral  springs  g,  g,  are  provided  for  sup- 
porting the  pole  in  the  vertical  plane,  and 


FIG.  95. — BOSTON  TROLLEY  BASE  AND  POLE. 

help  to  keep  it  from  leaving  the  wire.  T, 
is  the  trolley  ;  H,  the  harp  ;  r,  the  attach- 
ment ;  and  P,  the  pole. 

A  simple  form  of  trolley  base  is  shown 
in  Fig.  96.     Here  the  pole  P,  is  supported 


216  ELECTRIC    STREET   RAILWAYS. 

in  a  fork  £ ,  carrying  two  lugs  /,  /,  con- 
nected on  each  side  of  the  pole  by  rods  to 
the  extremities  of  stout  spiral  springs. 
The  effect  of  these  springs  is  to  maintain 
the  trolley  pole  vertical  under  ordinary 
circumstances,  and,  when  the  pole  is 


FIG.  96. — FORM  OF  TROLLEY  BASE. 

pulled  down,  it  tends  to  return  to  the 
vertical  position  by  the  compression  of 
one  spring  and  the  distension  of  the  other. 
The  pole  and  springs  together  can  swing 
around  the  vertical  axis  upon  which  they 
are  mounted  so  as  to  accommodate  the 
trolley  to  curves. 


TKOLLEYS. 


217 


FIG.  97. — TROLLEY  POLE  AND  BASE. 

Other  forms  of  trolley  poles  and  bases 
are  shown  in  Figs.  97  and  98.     The  rnech- 


FIG.  98.— TROLLEY  BASE. 


anism  is   sufficiently   clear   in    each    case 
to  be  understood  by  a  mere  inspection. 


218  ELECTRIC    STREET   RAILWAYS. 

The  angle  which  the  trolley  pole  makes 
with  the  roof  of  the  car,  under  ordinary 
circumstances,  is  about  40°.  The  trolley 
wheel  is  ordinarily  pressed  upward  with 
a  force  of  about  30  pounds  weight  against 
the  wire. 


OF  THg 

(UNIT*  BHSITT) 


CHAPTEE  IX. 

TEOLLEY    LIKE    CONSTEUCTION". 

THE  poles  which  support  the  trolley 
wire  over  the  track  are  either  of  wood  or 
of  iron.  In  the  country,  wooden  poles  are 
frequently  employed,  while  in  cities  iron 
poles  are  preferred.  The  methods  most 
frequently  used  for  supporting  the  trolley 
wire  are  either  by  the  use  of  span  wires  or 
by  brackets.  Span-wire  construction  re- 
quires poles  in  pairs,  on  opposite  sides  of 
the  street,  while  bracket  suspension  only 
necessitates  a  single  line  of  poles  even  for 
double  tracks.  Where,  however,  bracket 
poles  are  used  for  double  tracks  they  are 
open  to  the  objection  of  requiring  to  be 

219 


220 


ELECTRIC    STREET    RAILWAYS. 


placed   in  the   middle  of   the  street,  thus 
tending   to   obstruct   traffic. 

Fig.    99,    shows   the   span-wire  system, 
with  two  iron  poles,  P,  JP,  made  of  three 


FIG.  99.— SPAN- WIRE  SUPPORT. 

tapering  lengths  of  iron  tube,  s,  s,  is  the 
span  wire,  commonly  of  No.  1  A.  W.  G. 
iron  wire ;  n,  n,  are  the  insulators  sup- 


TROLLEY    LINE    CONSTRUCTION. 


221 


ported  on  the  span  wire,  and  in  their  turn 
supporting  the  two  trolley  wires  over 
their  respective  tracks.  The  poles  are 


\ 


FIG.  100.— BRACKET  POLE  FOR  DOUBLE  TRACK. 

commonly  27  to  30  feet  long,  and  are 
buried  to  a  depth  of  6  feet,  being  usually 
set  in  concrete.  For  span- wire  construe- 


222  ELECTRIC   STREET   RAILWAYS. 

tion,  the  poles  are  commonly  set  slanting 
from  the  tracks  so  as  to  enable  them 
better  to  stand  the  strain  of  supporting 
the  trolley  wires. 


FIG.  101. — SINGLE-TRACK  BRACKET  SUPPORT. 

The  poles  for  the  bracket-support  system 
are  always  set  vertically  and  midway  be- 
tween the  tracks.  Such  a  pole  is  shown 
in  Fig,  100.  Here  b,  b,  is  the  bracket  arm 
and  n,  n,  the  insulators  suspended  there- 


TROLLEY   LINE   CONSTRUCTION.  223 

from,  supporting  in  their  turn  the  trolley 
wires  w,  w>  and  w,  w. 

Forms  of  single-frack  bracket  suspension 
are  shown   in   Figs.    101    and    102.     The 


FIG.  102.— SINGLE-TRACK  BRACKET  SUPPORT. 

poles  are  set  about  120  feet  apart ;  i.  e., 
about  45  per  mile  with  bracket  suspen- 
sions, or  90  per  mile  for  span- wire  sus- 
pension. 

In  order  to  attach  the  span  wires  to  the 


224  ELECTRIC   STREET   RAILWAYS. 

iron  pole,  iron  clamps  are  employed, 
generally  of  the  form  shown  in  Fig.  103. 
When  the  clamps  are  in  position  facing 
each  other  on  opposite  sides  of  the  street, 
the  span  wires  are  stretched  between  them 


FIG.  103.— POLE  CLAMP. 

under  considerable  tension,  depending 
upon  the  weight  of  trolley  wire,  but  500 
pounds  weight  is  a  fair  tension.  Where 
only  a  single  span  wire  crosses  the  street, 
it  is  often  stretched  between  insulators  at 
the  top  of  the  poles>  as  shown  in  Fig.  99. 

Since,  of  course,  the  trolley  conductor  is 


TROLLEY   LINE   CONSTRUCTION.  225 

an  uninsulated  wire,  guard  wires  are  often 
employed  to  prevent  damage  from  con- 
tact with  bare  telegraph  or  telephone 
wires,  which  would  thereby  become  con- 
nected with  a  pressure  of  500  volts. 
Guard  wires  are  of  two  kinds ;  viz.,  span 
guard  wires,  which  cross  the  street  im- 
mediately above  the  span  supports  over 
the  trolley  wire,  and  running  guard  wires, 
which  run  parallel  with  and  immediately 
over  the  trolley  wires  to  receive  and  inter- 
cept any  wire  falling  from  above.  The 
relative  position  of  guard  and  suspension 
wires  is  illustrated  in  Fig.  104.  P,  P,  are 
opposite  poles,  c,  c,  the  pole  clamps, 
s,  s,  the  suspension  span  wire,  and  g,  g, 
the  guard  span  wires.  The  trolley  wires 
are  always  suspended  from  the  lower 
wire  s,  s,  and  guard  wires  are  usually  sus- 
pended over  the  trolley  from  the  upper 
span  ff,  g. 


226 


ELECTRIC    STREET   RAILWAYS. 


We  will  now  turn  our  attention  to  the 
devices  adopted  both  for  supporting  the 
trolley  wire  from  the  suspension  span  wire, 
and  for  enabling  the  trolley  to  be  stretched 


FIG.  104. — POLES  WITH  GUARD  AND  SUSPENSION  SPAN 
WIRES. 

tightly.  It  is  necessary  not  only  to  sup- 
port the  wire  rigidly  and  to  insulate  it  from 
the.  span  wire,  but  also  to  employ  devices 
for  this  purpose  that  shall  be  as  small  and 
sightly  as  possible.  The  simplest  way  tc 


TROLLEY    LINE   CONSTRUCTION. 


227 


support  a  trolley  wire  from  a  span  wire  is 
by  means  of  a  trolley  ear  or  insulator. 
Such  a  form  of  ear  or  insulator  is  shown  in 
Fig.  105.  e,  e,  is  a  metal  casting,  called 


FIG.  105. — STRAIGHT-LINE  SUSPENSION,  AND  TKOLLEY 
EAR  AND  INSULATOR. 

the  ear.  It  is  furnished  with  a  narrow 
edge  s,  Sj  having  tips  which  are  bent  and 
soldered  over  the  trolley  wire,  which  lies  in 
a  groove  extending  under  the  entire  length 
of  the  ear.  /,/,  is  the  body  of  the  suspen- 


228 


ELECTRIC    STREET   RAILWAYS. 


siou,  having  two  flanges  at  its  extremities 
as  shown.  The  suspension  span  wire  lies 
in  these  flanges  and  around  the  head  of  the 
insulator.  The  insulator  is  made  in  two 


FIG.  106. — TROLLEY  EAR  AND  SUSPENSION. 

parts,  A  and  B,  shown  separately  above, 
A,  being  an  insulating  cap  and  £>,  an  insu- 
lating cone.  These  two  parts  are  screwed 
together  and  grip  the  body  between  them. 
Fig.  106  shows  another  form  of  street  line 


TROLLEY   LINE   CONSTRUCTION.  229 

suspension  and  ear,  differing  from  the 
former  merely  in  details  of  construction. 
The  outer  iron  cap  G,  has  the  cover  v, 
screwed  down  upon  it  in  such  a  manner  as 
to  enclose  the  insulating  tube  t.  This  insu- 
lating tube  encloses  in  its  turn  the  bolt 
which  is  screwed  into  the  ear.  The  sus- 


FIG.  107. — DOUBLE-CURVE  SUSPENSION. 

pension  span  wire  is  gripped  tightly  be- 
tween the  flanged  projections  f,f,  of  the 
body  and  the  outside  of  the  iron  cap  c. 

A  great  variety  of  line  suspensions  are 
employed.  Fig.  107  shows  a  common  form 
called  a  double-curve  suspension,  named 


230  ELECTEIC   STREET   RAILWAYS. 

from  the  two  lugs  of  the  hood  or  cover. 
On  the  insertion  of  this  form  of  suspension, 
the  span  wire  has  to  be  cut  and  the  two 
ends  fastened  into  the  rings  r,  r.  In  other 
respects  the  suspension  is  practically  the 
same  as  that  shown  in  Fig.  106.  The 


FIG.  108. — SINGLE-CURVE  SUSPENSION. 

double-curve  suspension  possesses  the  ad- 
vantage that  all  the  tensions  exerted  upon 
it,  with  the  exception  of  that  produced  by 
gravitation,  are  exerted  in  the  horizontal 
plane ;  that  is  to  say,  the  span  wire  pulls 
sideways  upon  it  in  almost  the  same  plane  as 
the  tension  of  the  trolley  wire  lengthways. 


TROLLEY   LINE   CONSTRUCTION.  231 

Another  form  of  suspension,  called  the 
single-curve  suspension  is  shown  in  Fig. 
108.  This  suspension  is  introduced  at 
curves  in  the  track  or  line  where  only  a 


e 

^^BB^HBRsss 

«H 

FIG.  109. — BRACKET  SUSPENSION  EAR. 

single  pull  is  exerted  on  the  trolley  wire, 
instead  of  requiring  a  span. 

A   form    of   bracket   suspension  ear,  is 
shown  in  Fig.  109.     Here  the  cylinder  (7, 


232  ELECTRIC   STREET   RAILWAYS. 

is  damped  firmly  by  the  screw  clamp  P, 
upon  a  bracket  arm,  while  from  the 
cylinder  is  supported  the  insulator  7J  and 
ear  e  e,  upon  the  bolt  b  b. 

'When  two  lengths  of  trolley  wire  have 
to  be  connected  together,  the  connection  is 
always  made  at  an  ear,  or  point  of  support. 


FIG.  110.— SPLICING  EAR. 

Such  an  ear  is  for  this  reason  called  a 
splicing  ear.  A  form  of  splicing  ear  is 
shown  in  Fig.  110.  The  two  ends  to  be 
connected  are  brought  respectively  to  the 
ear  at  w  and  w',  under  the  grooves  to  x  and 
x',  and  then  through  the  holes  in  the  ear  at 
the  openings  o  and  o.  The  wires  are 
then  soldered  in  at  w,  x  and  o.  The 


TROLLEY   LINE   CONSTRUCTION.  233 

ear   is   bolted  to  its  supporting  insulator 
at  B. 

Instead  of  soldering  the  ends  of  the 
wire  in  a  splicing  ear  they  may  be  clamped 
in  a  device  called  an  automatic  ear,  shown 
in  Fig  111.  Here  the  two  wires  are  laid 


FIG.  111. — AUTOMATIC  OR  CLAMP-SPLICING  EAR. 

in  the  jaws  of  the  clainp  at  O,  C.  The 
jaws  are  then  pressed  together  and  secured 
by  a  bolt. 

The  necessity  for  maintaining  a  taut 
trolley  line,  so  as  to  ensure  a  good  and 
continuous  contact  with  the  trolley  wheel, 
requires  that  the  line  be  anchored  about 


234 


ELECTRIC    STREET   RAILWAYS. 


every    1,000  feet.     An   anchor-strain  ear 
is   shown   in   Fig.  112.     Strain  wires  are 

a  b 


FIG.  112. — ANCHOR-STRAIN  EAR. 

attached  to  the  lugs  a  and  £,  and  are  made 
fast,  through  insulators,  to  equidistant 
poles  as  shown  in  Fig.  113.  The  insula- 


FIG.  113.— ANCHORING  FOR  SINGLE  AND  DOUBLE  TRACK. 


TKOLLEY   LINE   CONSTKUCTION.  235 

tors  which  are  employed  for  this  purpose 
are  called  strain  insulators,  and  are  of 
various  forms.  A  common  form,  is  shown 
in  Fig.  114.  The  two  lugs  are  cast  into  a 
spherical  insulating  mass. 


FIG.  114. — STRAIN  INSULATOR. 

Trolley  wire  insulators  have  two  func- 
tions to  fill ;  namely,  a  mechanical  function  ; 
i.  e.,  in  providing  an  adequate  support, 
and  an  electrical  function ;  i.  e.,  as  an  elec- 
trical insulator.  In  order  to  be  sufficiently 
strong,  suitable  material  must  be  employed 
and  so  arranged  as  safely  to  support  the 
stresses  exerted  upon  it.  From  an  electri- 
cal point  of  view,  the  insulation  afforded 
by  an  insulator  is  never  that  of  the  mater- 


236  ELECTRIC    STREET   RAILWAYS. 

ial  of  which  the  insulator  is  formed,  and 
is  always,  in  practice,  the  insulation  of  the 
surface.  That  is  to  say,  the  electric  leak- 
age, which  takes  place  through  an  insulator, 
is  practically  all  over  the  surface  of  the 
insulator,  scarcely  any  passing  through  the 
substance  of  which  it  is  formed.  The  con- 
dition of  the  surface,  therefore,  greatly 
affects  the  efficient  action  of  the  insulators ; 
for,  if  dirty  or  dusty,  a  thin  film  of  moist- 
ure will  entail  a  considerable  electric 
leakage.  Assuming  the  same  surface  con- 
ditions, a  spherical  insulator,  such  as  that 
shown  in  Fig  114,  would  permit  consider- 
ably greater  leakage  than  a  cup  insulator 
of  the  type  shown  in  Fig.  106,  especially 
in  wet  weather.  The  electric  leakage, 
however,  which  can  be  permitted  on  a 
trolley  system  is  far  in  excess  of  that 
which  can  be  allowed  on  a  telegraph  or 
telephone  circuit;  since,  if  the  total  line 


TROLLEY   LINE   CONSTRUCTION.  237 

leakage  gave  rise  to  a  loss  of  activity 
amounting  to  1  KW,  which  would  represent 
a  total  leakage  current  of  2  amperes  under 
a  pressure  of  500  volts,  or  a  total  insulation 
resistance  of  only  250  ohms;  the  cost  of 
this  would  be  one  or  two  cents  per  hour. 
The  insulation  of  trolley  systems  usually 
averages  from  2,000  to  100,000  ohms  to 
the  mile  according  to  the  weather. 

When  a  trolley  road  branches,  it  is 
necessary  to  branch  the  trolley  wire. 
This  is  accomplished  with  the  aid  of  a 
device,  called  a  trolley  frog.  Fig.  115, 
shows  three  forms  of  trolley  frogs.  At  A, 
is  a  V-frog,  or  simple  two-way  frog,  in  an 
inverted  position,  so  as  to  show  the  guides. 
#,  is  a  metallic  guide  on  the  side  of  the 
single  track,  and  b  and  c,  are  the  two 
guides  on  the  side  where  the  road  bifur- 
cates. When  the  car  has  to  be  driven, 


238 


ELECTRIC    STREET    RAILWAYS. 


say  from  a  to  b,  the  rails  on  the  track  are 
so  switched  as  to  carry  the  car  in  that 
direction,  and  the  trolley  follows  from  the 


FIG.  115. — TROLLEY  FROGS. 


guide  a,  to  the  guide  b.  During  the  pass- 
age from  the  guide  a,  to  guide  b,  the  trolley 
wheel  will  either  maintain  contact  with 
the  line  through  its  metal  frame,  or  may 


TROLLEY   LINE   CONSTRUCTION.  239 

make  a  momentary  flash  at  the  point  of 
crossing.  B,  shows  an  inverted  right- 
hand  frog  and  C  an  inverted  left-hand 
frog.  Where  a  line  divides  into  three 
branches  special  frogs,  called  three-way 
?,  have  to  be  employed. 


B 

4* 

FIG.  116. — TROLLEY  CROSSING. 

At  the  intersection  of  two  streets  where 
trolley  wires-  necessarily  cross  each  other, 
the  crossing  is  effected  through  the 
medium  of  a  device  similar  to  a  frog, 
and  called  a  trolley  crossing.  Forms  of 


240  ELECTRIC    STREET   RAILWAYS. 

trolley  crossings  are  shown  in  Fig.  116. 
A,  is  a  right-angle  crossing,  and  B,  an 
acute-angle  crossing.  The  trolley  wires 
are  soldered  in  the  groove  over  the  four 
guides,  and  as  a  result,  the  trolley  wheel 
has  to  drop  slightly  at  a  crossing  to  pass 
beneath  the  guides.  Special  forms  of 
crossings  are  employed  when  it  is  desired 
to  insulate  the  two  crossing  trolley  wires 
from  each  other. 

Trolley  wires  are  made  in  all  sizes  from 
No.  4  A.  W.  G.,  with  a  diameter  of  0.204", 
to  No.  000  A.  W.  G.,  with  a  diameter  of 
0.410".  The  commonest  size  is  No.  0, 
of  0.3249"  diameter.  The  material  is 
usually  hard-drawn  copper,  although 
alloys  are  occasionally  used.  A  No.  0, 
hard-drawn  copper  wire  will  safely 
bear  a  tension  of  2,500  Ibs.  weight,  and 
usually  breaks  at  a  tension  of  5,000  Ibs. 


TROLLEY  LINE  CONSTRUCTION.     241 

weight.  A  hard-drawn  copper  wire  of 
this  size  has  a  resistance  of,  approximately, 
0.52  ohm  at  60°  F.,  its  resistance  being 
about  2  1/2  per  cent,  in  excess  of  the  re- 
sistance of  the  same  size  wire  in  soft 
copper,  whereas  silicon-bronze  wire  has 
sometimes  about  21/2  times  the  resist- 
ance of  the  same  size  of  soft  copper  wire. 


CHAPTER  X. 

TRACK    CONSTRUCTION. 

IT  is  frequently  a  matter  of  surprise 
that  the  installation  of  a  trolley  road  is 
almost  invariably  attended  by  the  recon- 
struction of  the  track.  The  necessity  for 
this  reconstruction  is  to  be  found  in  the 
fact  that  electric  cars  are  much  heavier 
than  ordinary  horse  cars,  and  contain  run- 
ning machinery  which  is  liable  to  injury 
from  excessive  jolting.  This  liability  to 
injury  from  a  weak  and  inferior  track  is 
increased  by  the  greater  speed  at  which 
electric  cars  run.  Moreover,  in  a  badly 
constructed  track  difficulty  is  experienced 
in  maintaining  an  efficient  running  contact 

242 


TRACK   CONSTRUCTION.  243 

between  the  trolley  and  the  trolley  wire. 
For  these  reasons  the  construction  of  the 
roadbed  and  track  requires  careful  at- 
tention. 

In   cities   more    care    and    expense   are 
naturally  taken  with  both  line  and  track 


FIG.  117. — TRACK  CONSTRUCTION. 

construction  than  in  the  open  country,  but 
the  tendency  is  towards  the  employment 
of  a  steel  girder  rail  weighing  90  Ibs.  per 
yard.  These  rails  are  laid  directly  on 
wooden  sleepers  to  which  they  are  spiked. 
This  construction  is  shown  in  Fig.  117, 
where  the  girder  rails  R,  R,  are  spiked  to 


244 


ELECTRIC    STREET   RAILWAYS. 


the  sleeper  S,  S,  and  are  also  bound  to- 
gether by  the  tie  rod  Ty  2}  the  roadbed 
being  paved  in  this  case  with  Belgian 
blocks.  The  rails  are  laid  with  their  ends 
close  together,  no  difficulty  having  been 
experienced  from  expansion  in  summer 


FIG.  118. — TRACK  AND  SLEEPERS,  SHOWING  METHOD  OF 
BREAKING  JOINTS. 

time.  It  is  common  to  break  these  joints 
so  that  the  joints  of  the  rails  on  one  side 
of  the  track  shall  come  opposite  to  the 
middle  of  the  rail  on  the  opposite  side. 
This  is  represented  in  Fig.  118,  where 
<7,  e/,  </,  and  J"',  </',  show  the  relative 
positions  of  the  joints  of  each  rail.  The 


TRACK   CONSTRUCTION.  245 

sleepers  in  this  case  are  also  so  distributed 
as  to  be  closer  together  near  the  joints,  as 
shown,  fy  f,  is  the  fish-plate  with  twelve 
bolts  which  pass  through  the  rail  and  are 
screwed  up  against  a  similar  fish-plate  on 
the  other  side  of  the  rail. 

With  the  use  of  a  ground  return  it  is 
necessary  to  ensure  as  intimate  a  contact  be- 
tween the  rails  as  possible,  so  as  to  secure 
a  continuous  metallic  path  and  to  lessen 
the  resistance  that  would  otherwise  be 
introduced  into  the  circuit.  Mere  contact 
of  the  ends  of  the  rails  with  their  connect- 
ing fish-plates  is  not  sufficient,  since  rust  at 
this  surface  produces  a  very  considerable 
resistance.  In  order  to  avoid  this,  various 
methods  of  bonding  the  rails  have  been 
proposed.  This  is  attempted  in  a  variety 
of  ways,  but  the  object  is  always  to  secure 
a  permanent  metallic  connection  between 


246 


ELECTRIC    STREET   RAILWAYS. 


successive  rails.  One  of  these  rail  bonds 
is  represented  in  Fig.  119.  To  use  this 
bond  the  rails  are  drilled  close  to  the  fish- 
plate and  a  bent  copper  rod  of  the  shape 
shown  at  A,  has  its  two  ends  pressed  into 
the  holes,  one  end  in  each  rail.  A  section 


FIG.  119. — CHICAGO  RAIL  BOND. 

of  the  rail  with  the  end  of  the  copper  rod 
projecting  through  it  is  shown  at  a.  The 
plug  B,  is  then  driven  with  the  hammer 
into  the  opening  of  the  rod  so  as  to  wedge 
it  tightly  into  the  iron  rail.  A  cross-section 
of  the  rail,  rod  and  plug  is  shown  at  G. 


TRACK   CONSTRUCTION.  247 

A  somewhat  similar  method  of  effecting 
a  rail  bond  consists  in  the  use  of  stout 
copper  wire  in  place  of  the  copper  rod. 
Here  the  wire  is  passed  twice  through 
holes  in  the  rail  each  side  of  the  fish  plates 
and  copper  wedges  are  driven  in  so  as 


FIG.  120.— WIRE  RAIL  BOND. 

completely  to  wedge  the  wire  against  the 
metal  rail.  At  intervals  this  wire  is 
led  directly  across  the  track  and  enters 
into  a  bond  with  the  other  rail,  thus  effec- 
tively connecting  the  two  rails  together. 
A  wire  bond  of  this  character  is  shown  in 
Fig.  120. 


248  ELECTRIC    STREET   RAILWAYS. 

The  most  efficient  bond  from  a  purely 
electric  point  of  view  is  the  welded  rail 
bond  obtained  by  welding  the  rails  together. 
For  this  purpose  a  very  powerful  electric 
current  is  passed  through  the  ends  of  the 
rails,  and  pieces  of  iron,  called  chucks, 
which  are  used  in  place  of  the  fish-plates. 
When  completed,  this  joint  is  as  solid  and 
strong  as  the  rest  of  the  rails,  thus  afford- 
ing a  practically  continuous  iron  rail,  and 
therefore  a  continuous  return  circuit. 
Another  method  of  accomplishing  the 
same  result  consists  in  pouring  melted  cast 
iron  around  the  ends  of  the  rails  after 
cleaning  them,  and  so  effecting  a  solid 
joint.  Although  success  has  not  yet  been 
perfectly  obtained  with  continuous  rails, 
yet  it  would  appear  that  the  stresses  pro- 
duced by  expansion  and  contraction  in  a 
uniform  continuous  rail  are  well  within  the 
limits  of  the  elasticity  of  the  steel. 


OF  THE 


CHAPTER  XL 

ELECTROLYSIS. 

WHEN  an  electric  current  is  sent  through 
a  vessel  containing  ordinary  tap  water,  the 
passage  of  the  current  is  attended  with  the 
decomposition  of  the  water  into  its  con- 
stituent elements,  oxygen  and  hydrogen. 
These  elements  are  liberated,  in  the  gaseous 
state,  only  at  the  points  of  entrance  and 
exit  of  the  current  from  the  water,  the 
hydrogen  beiug  liberated  where  the  cur- 
rent leaves  the  water,  and  the  oxygen 
where  the  current  enters  the  water.  If 
the  conducting  surface  at  which  the  cur* 
rent  enters  is  oxidizable  like  iron,  copper, 
lead,  zinc,  and  nearly  all  ordinary  metals 

249 


250  ELECTRIC    STREET    RAILWAYS. 

it  becomes  corroded  or  oxidized,  while  a 
similar  metal  surface  or  electrode  provided 
for  the  exit  of  the  current  from  the  water 
is  unaffected,  the  hydrogen  being  usually 
disengaged  in  bubbles.  Decomposition 
effected  in  this  manner,  by  an  electric  cur- 
rent, is  called  electrolytic  decomposition,  and 
the  corrosion  of  metals  in  liquids  in  this 
manner  is  called  electrolytic  corrosion. 

The  earth  or  ground  is  only  capable  of 
acting  as  a  return  circuit  by  virtue  of  the 
moisture  which  is  practically  always  pres- 
ent. Consequently,  in  all  cases  where  the 
ground-return  circuit  is  used,  the  metallic 
surfaces  by  which  the  current  enters  and 
leaves  the  ground  are  liable  to  electrolytic 
action.  Where  the  current  leaves  the 
metallic  conductors  to  enter  the  ground,  or 
the  moisture  within  the  ground,  there  will 
be  electrolytic  corrosion,  but  where  the 


ELECTROLYSIS. 


251 


current  enters  a  metallic  conductor  on 
leaving  the  ground  there  will  be  no 
electrolytic  corrosion,  although  there  may 
be  a  liberation  of  hydrogen.  On  the  con- 
trary, there  will  be  an  electric  protec- 
tion afforded  the  metal,  at  such  points — the 


FIG.  121.— SIMPLE  TROLLEY  CIRCUIT. 

oxidation  being  less  than  that  of  similar 
metal,  exposed  to  ordinary  conditions  in 
the  absence  of  electric  currents. 

The  simplest  condition  of  a  trolley  sys- 
tem is  represented  in  Fig.  121.     Here  the 


252  ELECTRIC    STREET   RAILWAYS. 

generator  6r,  has  its  positive  pole  con- 
nected to  the  trolley,  that  is,  the  current 
enters  the  trolley  from  the  generator,  passes 
through  the  car  motors,  and  returns  to  the 
generator,  partly  by  the  track  and  partly 
by  the  ground ;  i.  e.,  the  water  in  the 
ground,  as  a  supplementary  or  auxiliary 
conductor.  If  the  track  had  no  electric 
resistance,  or  conducted  perfectly,  all  the 
current  would  return  through  the  track 
and  none  would  pass  through  the  ground. 
If,  on  the  other  hand,  the  track  were  dis- 
connected at  some  point,  for  instance  at 
each  rail  joint,  then  its  resistance  would  be 
indefinitely  great  and  practically  all  the 
current  would  pass  through  the  ground. 

The  better  the  electric  conditions  of  the 
rail  bonds,  and  the  lowrer  the  resistance  of 
the  track,  the  greater  will  be  the  pro- 
portion of  the  current  which  will  pass 


ELECTROLYSIS.  253 

through  the  track  and  the  less  the  propor- 
tion which  will  pass  through  the  diffused 
circuits  in  the  ground.  Where  the  current 
leaves  the  rails  on  the  track,  to  enter  the 
ground,  there  will  be  corrosion  or  oxidation 
of  those  rails,  but  where  the  current  re- 
turns from  the  ground  to  the  track,  or  other 
buried  metal  at  the  power  house  connected 
with  the  generator,  there  will  be  no  corro- 
sion, and  even  a  tendency  to  prevent  corro- 
sion. 

When  electrolytic  corrosion  takes  place 
the  amount  is  perfectly  definite.  One 
coulomb  of  electricity  passing  through 
water  will  dissolve  0.000,002361  Ib.  of 
lead  electrode,  and  0.000,000,6393  Ib.  of 
iron  electrode.  Since  an  ampere*  is  a  rate 
of  flow  of  one  coulomb-per-second,  a  cur- 
rent strength  of  one  ampere  will  dissolve 
0.000,002361  Ib.  of  lead  per  second,  or 


254  ELECTRIC    STREET   RAILWAYS. 

0.000,000,6393  Ib.  of  iron  per  second,  and 
therefore,  if  an  ampere  be  steadily  main- 
tained for  one  year  it  will  dissolve  by  cor- 
rosion 74.46  Ibs.  of  lead  and  20.16  Ibs.  of 
iron.  If  the  current  be  increased  to  ten 
amperes,  the  amount  of  lead  or  iron  cor- 
roded will  be  ten  times  as  great,  the  chemi- 
cal action  being  directly  proportional  to 
the  quantity  of  electricity  which  is  passed. 

In  the  case  of  Fig.  121,  corrosion  will 
occur  over  the  surface  of  the  track  where 
it  lies  in  contact  with  moist  earth.  The 
corrosion  will  not  be  uniform,  but  will 
proceed  faster  at  some  points  than  others, 
the  rate  of  corrosion  depending  upon  the 
distribution  of  current  over  its  surface  ;  i.  e., 
on  the  local  facility  with  which  the  current 
escapes  into  the  earth.  The  total  amount 
of  electrolytic  corrosion  will  depend  only 
on  the  total  quantity  of  electricity,  in 


ELECTROLYSIS.  255 

ampere-hours    or   coulombs   passing   from 
the  metal. 


If,  however,  the  generator  has  its  nega- 
tive pole  connected  to  the  trolley  wire, 
and  its  positive  pole  connected  to  the 
track,  the  electrolytic  conditions  will  be 
reversed;  for,  the  current  will  now  leave 
the  metallic  surfaces  for  the  moist  ground 
in  the  vicinity  of  the  power  house,  and 
there  the  corrosion  will  take  place  to  an 
aggregate  amount  depending  entirely 
upon  the  total  quantity  of  electricity  pass- 
ing into  the  ground.  There  will  now  be 
no  corrosion  where  the  current  re-enters  the 
track. 

Were  the  corrosion  which  occurs  with 
street  .car  systems  limited  to  the  track,  the 
consequences  would  not  be  so  serious,  but 
in  cities  the  corrosion  affects  the  metallic 


256 


ELECTRIC    STREET    RAILWAYS. 


masses  of  the  gas  and  water  pipes,  and 
their  corrosion  may  lead  to  serious  damage. 
Fig.  122  diagrammatical!}7  represents  a 
street  car  system  in  which  the  positive  pole 
of  the  generator  is  connected  to  the  trolley, 
and  the  negative  pole  to  the  track.  This 


FIG.  122.— DIAGRAM  OF  TROLLEY  SYSTEM  IN  NEIGHBOR- 
HOOD OP  BURIED  PIPE.    NEGATIVE  POLE  GROUNDED. 

case  differs  from  that  of  Fig.  121,  only  in 
the  fact  that  a  system  of  water  pipes,  W, 
W,  is  supposed  to  lie  in  the  vicinity  of  the 
track.  If  we  suppose  that  a  current  of 
1 ,000  amperes  is  steadily  flowing  from  the 
generator  through  the  car  motors,  500 


ELECTROLYSIS.  257 

amperes  or  half  the  current  may  return 
directly  to  the  generator  through  the 
bonded  track,  100  amperes  may  return 
through  the  ground,  escaping  from  the 
track  at  more  distant  points  and  returning 
to  it  in  the  neighborhood  of  the  station, 
while  the  balance,  or  400  amperes,  may  find 
its  way  into  the  good  conducting  path  pre- 
sented by  the  system  of  water  pipes,  enter- 
ing it  in  the  distant  areas  and  leaving  it  in 
the  vicinity  of  the  power  house. 

Under  the  circumstances  above  men- 
tioned, there  will  be  electrolytic  action  at 
A,  where  the  current  leaves  the  track,  and 
at  B,  where  it  leaves  the  water  pipe.  The 
area  of  B,  will  be  a  comparatively  narrow 
one,  and,  consequently,  the  rapidity  of  cor- 
rosion will  be  comparatively  great,  since 
400  amperes  maintained  day  and  night, 
represents  a  total  corrosion  of  roughly 


258  ELECTRIC    STREET   RAILWAYS. 

8,000  pounds  per  annum  spread  over  a 
comparatively  small  area.  If  we  connect 
the  water  pipe  system  with  the  generator's 
grounded  terminal,  as  shown  by  the  dotted 
lines,  we  reduce  the  quantity  of  electricity 
which  leaves  the  surface  of  B,  through  the 
ground,  since  it  will  largely  pass  directly 
through  the  new  connection.  By  this 
means  the  electrolytic  corrosion  of  the 
water  pipes  will  be  diminished. 

If  the  negative  pole  of  the  generator  be 
connected  to  the  trolley  and  the  positive 
pole  be  connected  with  the  track,  as  shown 
in  Fig.  123,  then,  all  other  things  remaining 
the  same,  there  will  be  corrosion  at  A 
and  B  ;  namely,  at  the  portions  of  the  water 
pipe  remote  from  the  power  house  and 
at  the  portions  of  the  track  near  it.  In 
this  case,  however,  the  area  of  water  pipe 
over  which  the  corrosion  takes  place  is 


ELECTROLYSIS.  259 

more  extended,  and,  consequently,  the 
amount  of  corrosion  on  any  one  length  of 
pipe  in  the  district  will  be  correspondingly 
less. 


*-rA •***••  r* 

in*'-*  —  — •  /««-*  -  -  -  ~\~\  i 


1111 


w  W 

FIG.  123. — DIAGRAM  OP  TROLLEY  SYSTEM  IN  NEIGHBOR- 
HOOD OF  BURIED  PIPE.    POSITIVE  POLE  GROUNDED. 


There  are,  therefore,  two  methods  of 
dealing  with  the  dangerous  influences  of 
electrolytic  corrosion  upon  neighboring 
metallic  pipes.  The  first  is  to  ground  the 
positive  pole  of  the  generator  or  generators 
at  the  power  house,  and  so  spread  the  cor- 
rosion over  a  large  area  of  pipe  distant 


260  ELECTRIC    STREET    RAILWAYS. 

from  the  power  house,  trusting  to  the  en- 
larged area  and  the  slowness  of  corrosion 
to  avoid  serious  effects.  In  this  case  there 
is  no  advantage  to  be  gained,  so  far  as 
avoiding  corrosion  is  concerned,  by  directly 
connecting  the  water  pipe  system  with  the 
grounded  generator  terminal.  In  fact 
there  will  be  an  advantage  in  avoiding 
such  connections.  The  second  method  is 
to  ground  the  negative  pole  of  the  gener- 
ator at  the  power  house,  as  in  Fig.  122,  so 
as  to  bring  the  area  of  corrosive  action 
within  the  neighborhood  of  the  power 
house.  If  this  course  be  adopted  it  be- 
comes important  to  protect  this  area  by 
not  only  connecting  the  pipes  with  the 
grounded  generator  terminal,  but  also  by 
securing  good  electric  connections  between 
the  track  and  the  grounded  terminal  of  the 
generator  through  bonding  and  ground 
feeders. 


ELECTROLYSIS. 


261 


Whichever  method  be  adopted  the  use 
of  ground  feeders,  rail  welding,  and  effi- 
cient bonding  necessarily  reduces  the 
danger  of  corrosion  by  offering  a  better 


FIG.  124.— IRON  PIPE  CORRODED  BY  ELECTROLYSIS. 

metallic  conducting  path  to  the  return 
current.  Fig.  124  represents  a  piece  of 
pipe  destroyed  by  the  influences  of  electro- 
lytic corrosion. 


CHAPTEE  XII. 

SWITCHBOARDS. 

IF  we  trace  the  trolley  wires  of  any 
street  car  railway  system  we  will  find 
them  to  form  an  interconnected  network 
maintained  at,  approximately,  500  volts 
pressure  relatively  to  the  track.  From 
this  network  the  feeders  pass  to  the  power 
house,  either  suspended  overhead  on  poles 
and  insulators,  or  underground  through 
lead  covered  cables  placed  in  suitable  con- 
duits. Tracing  these  feeders  to  their 
origin  we  will  find  them  terminating  at 
what  is  called  the  switchboard.  The  use  of 
the  switchboard  is  to  enable  the  attendant 
at  the  power  house  to  learn  at  a  glance  the 


SWITCHBOARDS.  263 

electric  condition  of  the  system,  and  also  to 
enable  him  to  control  or  modify  the  electric 
condition  with  swiftness  and  convenience. 
To  this  end  the  switchboard  is  provided 
with  a  number  of  electric  measuring  in- 
struments, called  respectively  voltmeters, 
for  measuring  the  electric  pressure  in  volts, 
and  ammeters,  for  measuring  the  electric 
current  in  the  various  circuits  in  amperes. 

Fig.  125,  shows  a  form  of  railroad 
switchboard  intended  for  use  with  three 
separate  dynamo  generators  and  three 
separate  feeders:  This  switchboard  con- 
sists of  seven  vertical  panels  formed  of 
marble,  a  good  insulator.  The  three 
pauels  on  the  right  hand  are  feeder  panels, 
and  a  generator  is  connected  to  and  con- 
trolled by  each.  The  central  panel  is  a 
total-current  and  pressure  panel,  for  measur- 
ing the  entire  current  supplied  to  the  three 


264  ELECTRIC    STREET   RAILWAYS. 


FIG.  125. — SWITCHBOARD  FOR  RAILWAY  POWER  HOUSE. 


SWITCHBOARDS.  265 

feeder  panels,  and  the  main  pressure  of 
the  power  house.  /SJ  &,  $,  are  the  three 
generator  switches,  consisting  each  of  three 
metallic  knife  blades  maintaining  connec- 
tion between  metallic  clips.  In  the  posi- 
tion shown,  all  three  switches  are  closed 
and  all  three  generators  are  at  work  to- 
gether. Beneath  the  generator  switches 
are  rheostat  boxes,  R,  ~R,  H,  for  control- 
ling the  current  supplied  by  each  respective 
generator.  A,  A,  A,  are  automatic  circuit- 
breakers,  which  are  so  arranged  that  the 
current,  supplied  by  their  respective  gener- 
ators, passes  through  stout  coils  or  spirals 
of  copper  rod,  so  that  when  this  current 
strength  becomes  dangerously  great,  indi- 
cating an  overload  upon  the  generator,  the 
magnetic  action  of  the  spirals  releases  a 
lever,  which  under  the  action  of  the  spring 
flies  back  and  breaks  the  circuit.  M,M,M, 
are  three  ammeters,  each  in  circuit  with  its 


266  ELECTRIC    STREET   RAILWAYS. 

respective  generator,  so  that  the  pointer 
or  index  shows  at  a  glance  the  current 
strength  and,  therefore,  the  load  upon  that 
generator.  L,  L,  L,  are  lightning  arres- 
tors,  intended  to  carry  to  ground  any 
discharges  due  to  lightning,  thus  avoiding 
damage  to  the  system.  Turning  to  the 
feeder  panels,  s,  s,  s,  are  the  three  feeder 
switches.  On  closing  one  of  these  switches 
the  particular  feeder  which  supplies  it  is 
connected  with  the  generator  or  generators, 
which  may  be  in  use,  so  that  if  all  three 
of  the  switches  shown  be  opened,  the 
the  entire  load  will  be  taken  off  the  gene- 
rators, even  though  these  be  maintained 
running.  #,  ay  a,  are  automatic  feeder  cir- 
cuit-bredkerSy  similar  in  their  action  to 
those  already  alluded  to  at  A,  A,  A. 
/,  I,  I,  are  lightning  arrestors,  connected 
to  each  feeder,  similar  to  those  at  Z,  Z,  L. 
JVj  is  the  main  ammeter,  supplied  by  all 


SWITCHBOAKDS.  267 

three  generator  ammeters,  M,  M,  M,  to- 
gether, and  supplying  in  its  turn,  the 
various  feeders.  FJ  is  the  voltmeter 
showing  the  pressure  between  generator 
terminals  at  the  station  in  volts. 


The  automatic  cut-outs  A,  A,.  A,  and 
a,  a,  a,  are  constructed  as  shown  on  a 
larger  scale  in  Fig.  126.  The  current  sup- 
plied by  the  generator  passes  from  the 
clip  P9  with  its  attached  carbon  plate  JV, 
across  the  metal  frame  of  the  switch  H, 
to  the  opposite  metal  clip  P ,  and  its 
attached  carbon  plate  N',  thence  by  the 
terminal  A,  through  the  three  turns  of 
the  metallic  coil  or  spiral  (7,  to  the  terminal 
J?,  from  whence  it  passes  to  the  line.  On 
lifting  the  handle  Hy  into  the  position 
shown  on  the  left  hand,  a  metallic  connec- 
tion is  established  between  the  clips,  and 
the  switch  is  kept  in  position  by  a  detent. 


268 


ELECTRIC   STREET   RAILWAYS. 


The  current  passing  through  the  three 
turns  of  the  coil  C,  magnetizes  them  and 
tends  to  lift  the  iron  core  in  its  interior. 


FIG.  126.— CARBON-PLATE  AUTOMATIC  CIRCUIT-BREAKER. 

As  soon  as  the  current  strength  exceeds  a 
certain  limiting  safe  value,  the  raising  of 
the  iron  core  by  the  increased  magnetic 


SWITCHBOARDS.  269 

attraction  lifts  the  detent,  and  permits  the 
switch  H,  to  be  thrown  out  of  the  clips 
into  the  position  shown  on  the  right  hand 
side.  As  soon  as  connection  at  the  clips 
P,  P,  is  broken,  a  powerful  arc  would 
probably  form  which  might  melt  the 
switch.  Contact  is,  however,  maintained 
through  the  medium  of  the  carbon  plates 
JVJ  N,  and  the  carbon  rods  J?,  R,  which 
brush  against  them.  The  arc  which  takes 
place  when  this  latter  contact  is  broken  is 
a  carbon  arc,  instead  of  a  copper  arc,  and 
such  burning  as  does  occur  can  only  result 
in  burning  some  of  the  carbon  parts,  which 
can  be  readily  replaced  from  time  to  time. 

Another  form  of  automatic  circuit 
breaker  is  shown  in  Fig.  127.  Here  the 
circuit  is  normally  closed  from  the  terminal 
H,  through  the  three  turns  of  the  spiral  <?, 
the  metallic  projections  B,  B,  and  the 


270 


ELECTRIC    STREET    RAILWAYS. 


bridge  of  flexible  copper  strips  t,  t,  between 
them.  As  soon  as  the  current  strength 
passing  through  the  apparatus  exceeds  the 


FIG.  127. — MAGNETIC  CIRCUIT-BREAKER. 

limiting  amount  for  which  it  is  set,  the 
coil  O,  attracts  its  armature  against  the 
tension  of  the  spiral  spring  t,  and  permits 


SWITCHBOAKDS.  271 

the  larger  spring  S,  to  withdraw  the  bridge 
t,  t,  from  the  blocks  B,  B.  A  shunt  cir- 
cuit, is,  however,  retained  between  J3,  B, 
for  a  little  while  after  this  contact  is 
broken  through  the  two  magnet  coils 
M,  M,  and  a  smaller  set  of  contacts  in  the 
upper  part  of  the  apparatus.  The  magnets 
become  powerfully  excited  by  the  passage 
of  the  current  through  them  and  produce 
magnetic  poles  over  the  iron  surfaces 
jP,  Pj  P,  and  P,  one  pole  being,  say  north, 
and  the  other  south.  Between  these  pole 
pieces,  the  second  or  auxiliary  contact  is 
broken  by  the  descent  of  the  lever  £,  after 
the  main  contact  is  broken  at  B  B,  and  t. 
The  arc,  which  tends  to  follow  the  inter- 
ruption of  the  auxiliary  contact,  is  instantty 
extinguished  by  the  influence  of  the  mag- 
netic flux  between  the  polar  projections, 
as  already  explained  in  the  chapter  on 
controllers. 


272  ELECTRIC   STREET   RAILWAYS. 

Should  one  of  the  generators,  or  one  of 
the  feeders,  become  overloaded,  the  auto- 
matic circuit-breaker  will  open  its  circuit 
and  protect  the  generator  placed  therein. 
In  many  cases  the  overload  may  have  been 
due  to  an  accidental  temporary  short-cir- 
cuit, which  almost  immediately  disappears. 
In  such  cases  it  is  usual  to  reset  the  circuit- 
breaker  by  the  use  of  the  handle  H,  until 
it  is  found  that  after  three  trials  the  appa- 
ratus refuses  to  remain  set.  It  is  then 
usual  to  allow  the  circuit  to  remain  broken 
and  to  search  for  the  short-circuit. 

Fig.  128,  shows  a  form  of  ammeter,  such 
as  is  seen  at  M,  M,  M,  in  Fig.  125.  Here 
the  metallic  pieces  A,  B,  form  the  termi- 
nals of  the  massive  coil  C.  having  two 

o 

turns  placed  directly  in  the  circuit.  The 
iron  core  0,  is  attracted  towards  this  helix, 
by  the  electromagnetic  action  of  the  cur- 


SWITCHBOARDS. 


273 


rent,  this  attraction  increasing  with  the 
current  strength.  The  core  O,  is  suspended 
from  a  short  balance  arm  pivoted  at  v,  and 


V 


FIG.  128.— FORM  OF  AMMETER. 

having  a  long  pointer  or  index  p,  moving 
over  a  scale.  When  the  current  is  cut  off, 
the  counterpoise  overweights  the  iron  core, 
and  the  pointer  moves  into  a  position 


274  ELECTRIC    STREET    RAILWAYS. 

opposite  to  the  zero  point  on  the  left  hand 
of  the  scale.  As  the  current  strength 
through  the  coil  (7,  increases,  the  magnetic 
pull  tends  to  overcome  the  gravitational 
pull  on  the  counterpoise,  and  the  pointer 
moves  further  and  further  towards  the 
right. 

A  form  of  voltmeter,  shown  at  V,  in  Fig. 
125,  is  represented  on  an  enlarged  scale  in 
Fig.  129.  The  principle  and  action  of  the 
apparatus  are  similar  to  that  of  the  amme- 
ter in  the  preceding  figure.  The  principal 
difference,  however,  is  in  the  winding  of 
the  coil  Oy  which,  instead  of  consisting  of 
but  two  turns  carrying  a  powerful  current, 
has  very  many  turns  carrying  a  feeble  cur- 
rent. Resistances  of  insulated  wire  wound 
on  frames  JR  It,  are  placed  in  circuit  with 
the  vertical  coil  (7,  and  the  terminals  of  the 
generator.  The  current  strength  passing 


SWITCHBOARDS. 


275 


in  this  circuit  will  be  determined  by  Ohm's 
law.  For  example,  if  the  total  resistance 
of  the  coil  C,  and  the  two  resistances  H,  R, 


FIG.  129.— VOLTMETER. 


is  5,500  ohms,  and  the  pressure  at  the  gen- 
erator terminals  is  550  volts,  then  the  cur- 
rent strength  passing  through  the  circuit 


276          ELECTRIC    STREET    RAILWAYS. 

will  be  55Q   volts  =  — th  ampere    =    100 
5,500  10 

milliamperes.  The  counterpoise  t,  is  so  ar- 
ranged that  at  this  particular  current  the 
pointer^,  stands  vertical  and  indicates  550 
volts.  Should  the  pressure  rise  10  per 
cent.,  or  to  605  volts,  the  current  in  the 
circuit  of  the  coil  (7,  would  increase  10  per 
cent.,  and  its  increased  magnetic  attrac- 
tion on  the  iron  core  within  it  would 
deflect  the  pointer  to  a  position  which 
is  marked  605  volts  on  the  scale.  It  is 
evident,  therefore,  that  this  voltmeter  is 
essentially  an  ammeter  with  a  high  resist- 
ance in  its  circuit. 

The  general  connection  which  is  effected 
by  the  switches  on  the  switchboard,  omit- 
ting all  details  of  ammeters,  voltmeters, 
cut-outs  and  lightning  arresters,  is  diagram- 
matically  represented  in  Fig.  130.  Here 


SWITCHBOARDS. 


277 


two  main  bars,  or  bus-bars,  B  _Z?,  B'B' — a 
contraction  for  omnibus  bars,  so  called  be- 


B 


G, 


tf 

FIG.  130. — GENERAL  CONNECTION  BETWEEN  GENERATORS 
AND  FEEDERS  AT  POWER  HOUSE. 

cause  they  receive  the  entire  current  from 
the  generators, — are  connected,  one  to  the 
feeders  and  the  other  to  the  track,  ground 


278          ELECTRIC    STREET   RAILWAYS. 

feeders,  or  ground  connection.  Between 
these  bus-bars  the  station  pressure  of  say 
550  volts  is  maintained.  One  or  more  of 
the  generators  G^  G&  G&  are  connected 
across  the  bus-bars  according  to  the  amount 
of  load  on  the  lines ;  i.  e.,  according  to  the 
number  of  cars  that  are  running,  and  the 
work  they  are  doing.  If  only  a  few  cars 
are  on  the  line  the  current  required  will  be 
small,  the  electric  activity  small,  and  a 
single  generator  may  be  sufficient.  Thus 
the  switch  /Si,  may  be  closed,  leaving  G^  to 
take  the  entire  load.  If  more  cars  are  run 
the  total  current  strength  supplied  to  the 
feeders  may  require  the  addition  of  a  sec- 
ond generator  G2,  by  bringing  it  up  to 
speed  and  excitation  and  closing  the  switch 
$2,  and  so  on  for  the  other  generators. 


CHAPTER  XIII. 

GENERATORS    AND    POWEK    HOUSES. 


now  from  the  switchboards  to 
the  generators  which  supply  them,  we 
notice  two  distinct  types  ;  namely,  the  belt- 
driven  generator,  and  the  direct-driven 
generator;  i.  e.,  a  generator  directly  con- 
pled  to  the  driving  engine.  The  modern 
tendency  in  large  power  houses  is  to  em- 
ploy very  large  generators,  of  say  1,000 
HP  each,  and  to  connect  these  directly 
to  a  driving-engine.  In  some  power 
houses,  however,  belt-driven  generators 
are  employed.  The  belt-driven  generators 
have  usually  four  poles,  and  very  rarely 
have  less  than  this  number.  The  large 

279 


280          ELECTRIC    STREET   RAILWAYS. 

direct-driven  generators  have  usually  more 
than  four  poles,  since  it  is  found  more  con- 
venient and  economical  to  construct  gener- 
ators of  large  output  with  a  greater 
number  of  poles.  Fig.  131  shows  an 
example  of  a  belt-driven  generator  of  500 
KW  output.  Fig.  132  shows  a  direct- 
driven  generator. 

Turning  to  Fig.  131,  N9  S,  N,  8,  are  the 
four  magnet  poles  wound  with  coils  of 
insulated  wire.  In  nearly  all  cases  rail- 
way generators  are  compound-wound  /  i.  e., 
there  are  two  windings  on  each  coil,  one 
of  very  stout  conductor  and  of  very  few 
turns,  connected  directly  in  the  armature 
circuit,  the  other  of  many  turns  of  fine 
wire,  connected  in  a  shunt,  or  by-path 
around  the  armature.  The  object  of  com- 
pound winding  is  to  maintain  the  pressure 
automatically  constant  at  the  brushes,  or 


282  ELECTRIC    STREET   RAILWAYS. 

at  the  switchboard  bus-bars,  notwithstand- 
ing changes  in  the  number  of  cars,  or  load. 

The  armature  A,  revolves  within  the 
annular  space  provided  between  the  four 
pole- pieces,  and  with  it  the  commutator 
C.  On  the  surface  of  this  commutator 
four  sets  of  collecting  brushes  H,  H,  are 
fixed  on  a  frame,  capable  of  slight  adjust- 
ment in  angular  position  by  means  of  the 
wheel  shown  at  the  base  of  the  pedestal. 
T,  is  one  of  the  main  terminals,  with 
which  the  brushes  are  connected.  B,  is 
the  driving  belt. 

In  Fig.  132,  similar  letters  refer  to 
similar  parts.  Here  there  are  also  four 
poles  and  four  sets  of  brushes,  capable  of 
being  rotated  together  within  certain 
limits  by  the  projecting  handle.  The 
engine  E,  is  coupled  directly  to  the  arma- 


!"- 

J) 

a 
> 
u 


284  ELECTRIC    STREET   RAILWAYS. 

ture  shaft  through  powerful  springs  con- 
tained within  the  coupling  K.  F,  is  a 
fly-wheel  and  P,  a  cluster  of  six  incandes- 
cent lamps  in  series,  called  pilot  lamps. 


FIG.  133. — ARMATURE  OF  DIRECT-DRIVEN  GENERATOB. 

A  particular  armature  intended  for  a 
direct-driven  railroad  generator  is  shown 
in  Fig.  133.  Here  the  armature  consists 


GENERATORS   AND   POWER  HOUSES.      285 

of  two  distinct  parts ;  namely,  a  body  or 
core  of  iron,  and  conducting  wires.  The 
core  is  laminated,  that  is,  formed  of  a 
number  of  thin,  soft,  sheet-iron  discs,  pro- 
vided with  slots  in  their  external  edges,  so 
that  when  assembled  in  the  shape  of  a 
short  cylinder,  a  number  of  longitudinal 
slots  or  grooves  are  provided  for  the  recep- 
tion of  the  wires.  Without  considering 
the  winding  in  detail,  it  will  suffice  to  say 
that  the  conductors  are  laid  in  the  slots 
S9  S,  and  are  then  connected  to  the 
separate  bars  or  segments  of  the  commu- 
tator C,  C7  G.  Fig.  134,  shows  the  opera- 
tion of  winding  another  form  of  railway 
generator  armature,  with  the  wires  W,  W, 
passing  through  the  slots  of  the  iron  arma- 
ture core  A.  In  this  case  the  commutator 
is  not  yet  placed  on  the  shaft.  A  com- 
pleted armature  is,  however,  shown  below 
at  JB,  with  its  commutator  at  O. 


286  ELECTRIC    STREET   RAILWAYS. 

During  the  revolution  of  the  armature 
through  the  magnetic  flux  produced  by 
the  field  magnets  of  the  generator, 
E.  M.  Fs.  are  induced  in  the  winding,  and 
when  their  circuit  is  closed  through  the 
feeders  produce  currents  in  them.  The 
value  of  the  E,  M.  F.  developed  by  the 
armature  during  its  rotation,  depends 
upon  the  total  amount  of  magnetic  flux 
passing  through  the  armature  and  its 
wires,  the  total  number  of  wires  wound 
over  the  surface  of  the  armature  in  the 
various  grooves,  and  the  number  of  revo- 
lutions which  the  armature  makes  per 
minute ;  i.  e.,  its  rotary  speed.  The  cur- 
rent strength  which  a  given  armature  can 
maintain  steadily,  depends  upon  the  size 
of  the  wires ;  i.  e.,  upon  the  resistance  of 
the  armature  and  its  capability  of  readily 
disengaging  the  heat  developed  by  the 
current  in  that  resistance.  The  limiting 


288  ELECTRIC   STREET   RAILWAYS. 

current  strength  is  usually  determined  in 
practice  by  the  heating  of  the  armature, 
which  in  good  practice  does  not  exceed 
40°  C.  above  the  surrounding  air,  during 
continuous  running. 

Illustrations  of  generator  rooms  in 
power-houses,  employing  respectively  the 
belt-driven  and  direct-driven  types,  are 
shown  in  Figs.  135  and  136.  Fig.  135 
shows  the  interior  of  the  Fifty-second 
Street  power  house  of  the  Brooklyn  street 
railway  system,  containing  twelve  belt- 
driven  generators,  each  of  500  KW  ca- 
pacity, capable  of  a  total  output  of 
6,000  KW,  and  representing  12,000  am- 
peres at  500  volts ;  or,  approximately, 
11,000  amperes  at  550  volts.  These  gen- 
erators are,  however,  capable  of  standing 
a  considerable  overload  for  a  limited  time. 
The  switchboard  $  is  seen  on  a  gallery 
at  the  end  of  the  room. 


1 

5   « 

i  a 


290  ELECTRIC   STREET   RAILWAYS. 

A  view  of  the  interior  of  another  Brook- 
lyn railway  power  house  ;  namely,  that  at 
Kent  Avenue,  is  shown  in  Fig.  136.  Here, 
instead  of  being  placed  on  the  floor  beneath 
the  generators  and  connected  to  the  latter 
by  belts,  as  in  Fig.  135,  the  engines  are 
mounted  side  by  side  with  the  generators 
and  directly  coupled  to  the  armatures. 
There  are  four  large  generating  units  in 
the  room  of  the  type  shown  at  1,  2,  3  and 
4  respectively.  Each  generator  has  twelve 
magnet  poles,  between  which  revolves  the 
armature  -4,  with  its  commutator  C,  at  a 
speed  of  75  revolutions  per  minute.  The 
armature  is  driven  by  a  double  engine 
E,  JS.  The  engine  is  a  double,  horizontal, 
compound-condensing  engine,  the  generator 
being  placed  between  the  two  halves. 
f,  F,  is  the  engine  fly-wheel  placed  on 
the  main  shaft,  close  to  the  armature. 
Each  of  these  large  generators  has  a 


w 

ii 

f    Jd 
g    « 

w 


292  ELECTRIC    STREET   RAILWAYS. 

capacity  of  3,000  amperes  at  a  pressure  of 
550  volts,  representing  an  activity  at  full 
load  of  1,650  KW,  and  a  total  output, 
when  all  are  at  full  load,  of  6,600  KW,  or 
8,800  HP,  approximately.  The  switch- 
board 8,  is  seen  at  the  end  of  the  room 
through  the  fly-wheels  of  the  two  engines, 
on  the  left  hand  side  of  the  figure.  One 
of  the  generators  in  the  figure;  namely, 
No.  3,  is  shown  incomplete,  the  field  mag- 
nets being  not  yet  assembled.  The  most 
recent  development  in  street  railway 
practice  is  in  the  direction  of  powerful 
slow-speed  engines  and  direct-connected 
generators  of  this  type. 

Fig.  137,  shows  a  plan  view  of  the 
engine  and  generator  room  in  the  Delaware 
Avenue  railway  power  house  at  Phila- 
delphia. Here  the  general  plan  of  engines 
and  generators  is  similar  to  that  shown  in 


a1! 


294  ELECTKIC   STREET   RAILWAYS. 

Fig.  136.  There  are  four  generating  units 
marked  1,  2,  3,  4,  each  consisting  of  a 
1,650  KW,  12 -pole  generator,  with  its 
armature  keyed  to  the  shaft  of  a  large 
compound-condensing  engine  of  2,000  HP 
(about  1,500  KW),  arranged  in  two  parts, 
one  part  on  each  side  of  the  generator. 
S,  /8J  is  the  switchboard,  behind  which  the 
feeders  are  seen.  jP,  is  the  air-pump  con- 
nected with  all  the  engines,  and  5,  is  a 
small  300-KW  direct-driven  unit  for  light 
loads.  One  of  the  larger  generator  units 
is  said  to  have  operated  as  many  as  212 
cars  at  one  time.  If  working  at  full  load 
this  represents  a  mean  activity  of  8  KW 
per  car.  At  this  rate  all  four  units  could 
operate  850  cars.  Each  generator  will 
stand  the  application  of  full  load  without 
any  change  in  the  position  of  its  brushes, 
and  will  stand  an  overload  of  50  per  cent, 
with  a  slight  movement  of  the  same. 


II 


296  ELECTRIC    STREET   RAILWAYS. 

Fig.  138  shows  a  section  of  the  power 
house  represented  in  plan  in  Fig.  137. 
Here  E,  E,  shows  one  of  the  engines,  and 
g,  g,  one  of  the  large  generators  on  the 
lower  floor.  On  the  floor  above  are 
placed  the  boilers  in  two  rows,  one  on 
each  side,  with  an  auxiliary  6r,  G,  between 
their  fronts.  The  boiler  accommodation 
is  for  ten  batteries,  each  of  500  HP,  repre- 
senting an  aggregate  capacity  of  5,000  HP 
nominally.  B,  B,  are  the  boilers,  shown 
in  cross-section  on  the  right  hand  and  inside 
view  on  the  left.  The  steam  pipes  de- 
scend to  the  ceiling  of  the  generator  room, 
and  the  engine  exhausts  are  led  to  the 
cellar  where  they  are  dripped,  and  the  main 
exhaust  pipe  X,  X,  is  led  to  the  roof. 


CHAPTER  XIV. 

OPERATION    AND    MAINTENANCE. 

THE  amount  of  power  which  a  street 
car  requires,  depends,  as  we  have  seen, 
upon  its  size,  weight,  the  number  of  pas- 
sengers it  is  carrying,  its  speed,  and  the 
gradient  on  which  it  runs.  It  may  vary 
from  no  power,  when  running  down  hill, 
to  100  KW  when  climbing  a  steep  hill. 
It  is  often  a  matter  of  surprise  to  those 
who  have  been  accustomed  to  see  a  pair  of 
horses  pull  a  street  car  through  the  city 
streets,  that  power,  representing  say  more 
than  100  horses  acting  together,  may  be 
needed  on  occasions  to  propel  electric 
cars.  The  reasons,  however,  are  very 

297 


298  ELECTRIC   STREET    RAILWAYS. 

clear.  An  electric  car  weighs  from  15,000 
to  20,000  pounds  without  passengers, 
while  a  horse  car  weighs  only  about  5,000 
pounds  without  passengers.  The  electric 
car  will  carry  many  more  passengers  than 
a  street  car,  runs  at  a  greater  speed,  and 
will  climb  grades  impossible  to  be  sur- 
mounted by  two  horses. 

A  good  rule  to  remember  is  that  on  the 
average,  over  a  city  street  railroad  system, 
an  electric  street  car  takes  1  KW  for  every 
mile  per  hour  it  averages,  that  is  to 
say,  if  a  car  runs  at  8  miles  per  hour 
it  absorbs  roughly  8  KW  of  electric 
power ;  or,  in  1  hour,  would  absorb  a 
total  amount  of  work  equal  to  8  kilowatt- 
hours.  This  rough  estimate  is,  of  course, 
independent  of  the  power  required  to 
heat  the  car  when  electric  heating  is  em- 
ployed. 


OPERATION   AND   MAINTENANCE.         299 

The  output  of  a  station,  that  is,  the  load 
on  the  generators,  varies  markedly  at 
different  hours  of  the  day.  As  a  rule  the 
heaviest  load  occurs  in  the  morning  and 
evening  hours.  The  reason  for  the  in- 
creased load  is  not  only  because  a  greater 
number  of  cars  are  running  and  the  cars 
are  more  heavily  laden,  but  the  startings, 
which  require  considerable  power,  occur 
more  frequently  during  the  time  of  greatest 
load.  Fig.  139  shows  load  diagrams  taken 
in  Boston,  Mass.,  on  June  16-19,  1895. 
It  will  be  observed  that  the  load  varies 
from  practically  0  at  4  A.  M.,  to  12,000 
amperes  and  800  cars,  and  that  the  total 
activity  correspondingly  varies  from  nearly 
0  to  about  6,000  kilowatts. 

It  has  been  found  from  a  report  in  1894, 
of  232  American  electric  street  railways, 
operating  5,120  miles  of  track  with  a  total 


300 


ELECTRIC    STREET   RAILWAYS. 


capital  of  $316,700,000,  and  a  funded  debt 
of   $279,000,000,   that   the    operating   ex- 


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s 

10    11    12    1      2      a      4 

6     7     8     a     10   11  12 

FIG.  139.— LOAD  DIAGRAMS  AT  BOSTON,  JUNE  16-19,  1895. 


penses   were  62.8  per  cent,    of  the  gross 
receipts,  and  the   fixed   charges  22.9    per 


OPERATION   AND    MAINTENANCE.         301 

cent.,  leaving  a  net  income   of   14.3   per 
cent,  of  the  gross  receipts. 

The  power  required  to  be  installed  at 
the  power  house  varies  with  a  number  of 
local  conditions,  but  averages  20  KW  per 
car  in  use.  The  cost  of  installing  this 
power  is  about  $70  per  KW  for  steam 
plants,  including  engines  and  boilers,  and 
about  $30  per  KW  of  combined  steam  and 
electric  plant,  or  $100  per  KW  of  total 
machinery.  The  cost  of  the  electric 
equipment  of  a  car,  including  two  25  HP 
motors  and  controllers,  is  about  $1,000,  and 
the  cost  of  a  car  so  equipped  complete, 
roughly  $2,300.  The  line  construction 
costs  roughly  $5,000  per  mile  of  double 
track,  excluding  track  construction,  but 
varies  considerably,  under  different  condi- 
tions. The  total  expense  of  a  car  mile, 
i.  e.j  a  run  of  one  mile  per  car,  varies  of 


302  ELECTEIC   STREET   HALLWAYS. 

course  considerably  with  the  size,  the  kind 
of  system  and  the  nature  of  the  traffic,  but 
a  fair  average  may  be  considered  as  being 
from  15  to  25  cents  per  car  mile.  Of  this 
the  cost  of  supplying  electric  power  is  usu- 
ally only  from  1  cent  to  2  cents  per  car 
mile.  In  small  systems  all  these  costs  are 
likely  to  exceed  those  given. 

The  size  and  style  of  the  car  which  is 
adopted,  varies  with  the  nature  of  the 
traffic,  and  the  speed  at  which  the  car  is 
expected  to  run.  Under  some  conditions 
heavy  cars  running  slowly  are  desirable, 
while  in  others  light,  high-speed  cars  are 
preferable. 

The  population  per  mile  of  street  rail- 
way track  in  the  United  States  is,  approxi- 
mately, 4,600,  varying  between  3,000  in 
the  New  England  States,  and  10,000  in  the 


OPERATION   AND   MAINTENANCE.         303 

Southern  States.  In  Canada,  it  is  about 
11,600.  The  total  street  car  mileage  in 
the  United  States  is  about  6  per  cent,  of 
the  total  steam  railroad  mileage,  and  the 
gross  earnings  about  50  per  cent,  of  the 
total  passenger  steam  railroad  earnings. 

For  the  purpose  of  facilitating  repairs 
on  the  line,  special  wagons  drawn  by 
horses  are  employed,  called  tower  wagons, 
arranged  so  as  to  bring  the  workmen 
within  easy  access  of  the  trolley  wire. 
These  wagons  carry  a  light  platform, 
which  is  either  rigid  or  is  capable  of  being 
raised  and  lowered.  Both  the  frame  of  this 
wagon  and  its  tower  being  of  wood,  the 
men  working  upon  it  are  practically  insu- 
lated, except  in  wet  weather. 

In  latitudes  where  snow  falls  the  track 
is  kept  clear  by  an  electric  snow  sweeper. 


304 


ELECTRIC    STREET   RAILWAYS. 


One  of  these  snow  sweepers  is  shown  in 
Fig.  140,  where  the  track  has  been  swept  by 
the  rotation  of  the  brushes  of  the  car. 
Fig.  141  shows  one  of  these  cars  in  action. 


FIG.  140.— ELECTRIC  SNOW  SWEEPER. 

There  are  four  motors  on  one  of  these 
cars,  usually  of  25  HP  each.  Two  of  the 
motors  are  connected  with  the  driving 
axles  in  the  usual  way,  and  the  other  two 


OPERATION   AND    MAINTENANCE.         305 

are  wound  for  a  higher  speed  and  are  con- 
nected   so    as    to     drive    the    revolving 


FIG.  141. — SNOW  SWEEPER  IN  ACTION. 

brushes.  These  sweeping  brushes  are 
fixed  at  an  angle  of  45°  with  the  front  of 
the  car. 

The  overhead  trolley  system  has  been 
objected  to  in  cities  on  account  of  its 
unsightliness.  The  use  of  trolley  poles 


306  ELECTRIC    STREET    RAILWAYS. 

with  their  span,  guard,  and  trolley  wires 
are  certainly  far  from  being  a  pleasing 
ornament  to  the  streets  of  a  well  built  city. 
For  this  reason  attempts  have  been  made 
to  replace  the  overhead  trolley  system  by 
an  underground  or  conduit  system  of  trol- 
leys, and  also  by  storage-battery  propulsion. 
The  overhead  trolley  system  is,  however, 
considerably  more  economical  to  erect  and 
maintain  than  either  a  storage  battery  or 
conduit  system.  In  large  cities,  where  an 
increased  cost  is  preferred  to  the  unsightli- 
ness  of  the  overhead  trolley  system,  the 
underground  trolley  may  find  a  successful 
use.  It  is  already  being  tried  in  Washing- 
ton, D.  C.,  and  elsewhere  in  the  United 
States,  while  in  the  city  of  Buda  Pesth, 
Austria,  an  extended  system  of  under- 
ground trolley  roads  has  been  running 
successfully  for  several  years. 


€B 
Of  THE 
IVERSITT, 
MUFORHj* 


CHAPTEE  XV. 

STOKAGE    BATTERY    SYSTEMS. 

THE  admitted  unsightliness  of  the  over- 
head trolley  system  and  the  difficulty  of 
maintaining  efficient  operation  of  the 
underground  trolley,  under  all  conditions 
of  climate,  have  led  to  many  efforts  to 
obtain  a  self-contained  system  of  electric 
railways ;  that  is,  a  system  in  which  each 
of  the  cars  will  carry  its  own  electric 
driving  power.  In  the  early  history  of 
the  art  this  was  attempted  by  means  of 
the  primary  battery.  Primary  batteries 
are  now  recognized  as  being  altogether  too 
expensive  for  this  purpose,  owing  to  the 
fact  that  they  derive  their  motive  power 

307 


308  ELECTRIC    STREET   RAILWAYS. 

from  the  consumption  of  zinc  in  a  solution, 
a  fact  which  will  effectually  prevent  such 
batteries  from  competing  with  other  types 
of  motive  power  so  long  as  the  price  of 
the  zinc,  and  the  solution  in  which  it  is 
dissolved,  maintain  anything  like  their 
present  values. 

% 

The  nearest  approach  to  the  successful 
solution  of  the  problem  of  an  electrically 
propelled  car,  which  carries  its  own  stored 
electric  energy,  is  found  in  the  use  of  the 
secondary  or  storage  cell.  In  this  system 
the  storage  cells  derive  their  charge,  or 
stored  electric  energy,  from  electric  cur- 
rent supplied  to  the  cells  at  some  central 
station.  As  some  time  is  required  to 
charge  the  cells,  they  are  usually  removed 
from  the  car  to  receive  their  charge. 
Before  proceeding  to  the  general  descrip- 
tion of  the  storage  battery  equipment  of  a 


STORAGE  BATTERY  SYSTEMS.     309 

car,  a  brief  account  of  the  construction  and 
operation  of  storage  batteries  will  be 
necessary. 

A  great  variety  of  forms  have  been 
given  to  the  secondary  or  storage  cell.  In 
practically  all  cases,  the  material  of  which 
their  plates  or  elements  are  formed  is  lead. 
If  two  sheets  of  lead  be  immersed  in  a 
solution  of  dilute  sulphuric  acid,  and  an 
electric  current  be  sent  through  the  solu- 
tion from  one  plate  to  the  other,  an 
electrolytic  decomposition  will  occur, 
whereby  the  positive  plate,  or  the  plate  at 
which  the  current  enters,  becomes  oxi- 
dized, while  the  negative  plate,  or  that  at 
which  the  current  leaves  the  cell,  liberates 
bubbles  of  hydrogen  gas.  During  this 
process  a  C.  E.  M.  F.  is  set  up  in  the  cell 
amounting,  probably,  to  about  2.5  volts, 
and  every  coulomb,  or  ampere-second  of 


310  ELECTRIC    STREET   RAILWAYS. 

electricity,  which  passes  through  the  cell, 
does  work  in  it  amounting  to  2.5  volt- 
coulombs  or  2.5  joules.  At  a  rate  of  1 
ampere,  or  1  coulomb  per  second,  the  work 
so  expended  in  the  cell  would  amount  in 
one  hour,  to  3,600  X  2.5  ==  9,000  joules  or 
2.5  watt-hours. 

If  there  were  no  resistance  in  the 
cell;  and  if,  moreover,  no  free  hydrogen 
gas  escaped  from  it,  all  the  above 
work  would  be  expended  in  chemical 
action,  which  would  be  stored  up  in  the 
cell  in  the  form  of  chemical  products.  So 
far  as  the  C.  E.  M.  F.  is  due  to  the  drop 
of  pressure  through  the  resistance,  the 
work  is  expended  as  heat,  but  so  far  as  it 
is  produced  by  the  C.  E.  M.  F.  of  chemi- 
cal action,  it  is  theoretically  possible  to 
store  the  work  in  chemical  combinations. 
If  after  having  been  charged  in  this  way 


STORAGE   BATTERY    SYSTEMS.  311 

the  cell  is  removed  from  the  charging 
circuit  and  its  plates  are  connected 
through  a  wire,  it  will  act  as  a  primary 
battery ;  that  is  to  say  the  oxidized  plate 
will  behave  like  the  copper  plate  of  an 
ordinary  bluestone  cell,  and  the  unoxidized 
plate  like  the  zinc  of  such  a  cell. 

During  discharge,  the  E.  M.  F.  of  the  cell 
may,  perhaps,  average  2  volts,  and  each 
coulomb  of  electricity  supplied  through 
the  circuit  by  this  E.  M.  F.  represents  a 
delivery  of  2  joules  of  work.  During 
discharge,  and  the  performance  of  work, 
the  surface  of  the  oxide  on  the  posi- 
tive plate  becomes  partially  deoxidized, 
while  the  plain  lead  or  negative  plate 
becomes  partially  oxidized.  Finally, 
when  the  cell  is  completely  discharged, 
the  two  plates  are  superficially  the  same, 
each  being  partially  oxidized.  A  cell  is, 


312          ELECTRIC    STREET   RAILWAYS. 

however,  never  permitted  to  completely 
discharge.  In  order  to  restore  the  cell  to 
its  active  condition,  it  is  necessary  to  once 
more  charge  it  by  passing  through  it  the 
requisite  quantity  of  electricity. 

In  the  case  of  a  primary  cell,  in  which 
the  two  plates  or  elements  have  essentially 
different  chemical  composition,  the  com- 
plete discharge  is  accompanied  by  the  con- 
sumption of  one  of  the  plates ;  namely, 
the  zinc  plate.  It  is  impossible,  in  prac- 
tice, to  restore  the  active  condition  of  the 
primary  cell  by  sending  a  charging  cur- 
rent through  it,  and  the  plates  have  to  be 
renewed.  In  the  secondary  cell,  instead 
of  renewing  the  discharged  plates,  the 
electric  current  is  permitted  to  reverse 
the  chemical  changes  which  have  accom- 
panied discharge  and  thus  restore  the  active 
condition. 


STORAGE  BATTERY  SYSTEMS. 


313 


Instead  of  using  plain  lead  plates, 
special  forms  of  lead  plates  are  employed 
to  expose  a  very  large  surface  to  the 
active  liquid.  A  form  of  storage  cell  is 


FIG.  142. — FOKM  OF  STORAGE  CELL. 

shown  in  Fig.  142.  Here  the  glass  cell  or 
jar  C,  C,  contains  seven  flat  plates,  three 
of  which  are  connected  with  the  positive 
terminal  jP,  and  four  to  the  negative  termi- 
nal N.  The  solution  of  sulphuric  acid 


314 


ELECTRIC   STREET   RAILWAYS. 


and  water  is  poured  in  until  the  plates  are 
covered. 

A  positive  plate  is  shown  in  Fig.  143. 
Here  thirty-nine  circular  buttons,  or  discs 


I  •T'T 


FIG.  143. — POSITIVE  PLATE. 


of  peroxide  of  lead,  are  held  tightly  in  a 
frame  or  grid  of  antimonous  lead.  The 
addition  of  antimony  in  sufficient  quantity 
prevents  the  lead  grid  from  being  chemi- 


STORAGE  BATTERY  SYSTEMS.     315 

cally  attacked  by  the  solution  during 
charge  or  discharge.  Fig.  144  shows  a 
negative  plate,  with  sixty-four  square 
buttons  of  soft  porous  or  spongy  lead 


FIG.  144. — NEGATIVE  PLATE. 

similarly  held  in  an  antimonous  lead 
frame.  The  small  holes  in  the  centres 
of  the  buttons  play  no  part  in  the  action 
of  the  cell,  and  are  made  during  the 
mechanical  construction  of  the  buttons. 


316  ELECTRIC    STREET   RAILWAYS. 

The  principal  difficulty  which  has  been 
encountered  with  the  use  of  storage  cells 
in  electric  traction,  has  been  in  the  electric 
overloads  which  have  sometimes  been 
necessary,  and  which  greatly  decrease  the 
life  of  the  plates.  If  the  cars  invariably 
ran  upon  a  level  grade  and  their  load 
remained  uniform,  it  would  not  be  a  diffi- 
cult matter  to  ensure  an  absence  of  electric 
overloads,  or  undue  calls  for  power  upon 
the  batteries.  In  practice,  however,  owing 
to  the  existence  of  curves  and  grades 
and  over-discharging,  the  cells  are  gener- 
ally soon  injured,  so  that  their  mainten- 
ance becomes  very  expensive.  Moreover, 
the  great  weight  of  the  batteries  adds 
largely  to  the  non-paying  weight  of  the 
car.  Considerable  improvements  have, 
however,  recently  been  effected  in  the 
storage  battery  whereby  better  results 
may  be  expected. 


STORAGE   BATTERY   SYSTEMS. 


317 


A  form  of  storage  battery  car  truck  at 
present  in  use  on  Madison  Avenue,  New 
York  City,  is  shown  in  Fig.  145.  Here 
by  turning  the  motors  outwards  towards 
the  ends,  that  is  supporting  them  on  the 
opposite  side  of  the  axle  to  that  usually 
adopted,  the  space  A  B  G  D,  is  reserved 


FIG.  145. — STORAGE  BATTERY  TRUCK. 

in  the  centre  of  the  truck  for  the  recep- 
tion of  the  storage  battery.  A  truck  with 
a  storage  battery  in  place  is  shown  in  Fig. 
146.  In  this  truck  sixty  storage  cells  are 
arranged  in  two  batteries  of  thirty  cells 
each.  Since  the  mean  E.  M.  F.  of  dis- 
charge in  a  storage  cell  is,  approximately, 


318  ELECTRIC   STKEET   RAILWAYS. 

2  volts,  this  represents  a  pair  of  batteries 
each  having  an  E.  M.  F.  of  60  volts.  Each 
cell  has  400  ampere-hours  capacity ;  that 
is,  is  capable  of  supplying  40  amperes  for 
10  hours,  or  20  amperes  for  20  hours,  or  10 
amperes  for  40  hours,  etc.,  the  total  quan- 
tity of  electricity  being  400  X  3,600  = 


FIG.  146. — CAR  TRUCK  WITH  BATTERIES  IN  PLACE. 

1,440,000  coulombs.  The  above  men- 
tioned 1,440,000  coulombs,  representing  as 
they  do  the  capacity  of  its  battery,  should, 
theoretically,  be  discharged  whether  the 
duration  of  discharge  is  long  or  short,  that 
is  to  say,  whether  the  cells  are  allowed 
to  discharge  in  a  few  minutes  or  in  many 
hours. 


STORAGE  BATTERY  SYSTEMS.     319 

In  practice,  however,  there  is  always 
a  marked  diminution  in  the  avail- 
able quantity  of  electric  discharge  when 
the  duration  is  too  brief,  say  below  three 
hours.  If  the  E.  M.  F.  of  discharge  aver- 
ages 2  volts,  the  total  amount  of  energy 
available  from  each  cell  is  2  X  1,440,000 
=  2,880,000  coulomb-volts,  or  joules,  and 
60  such  cells  should  hold  a  total  quantity 
of  energy  of  172,800,000  joules.  Since  1 
watt-hour  is  3,600  joules,  and  1  KW  hour 
3,600,000  joules,  the  total  energy  in  the 
battery  is  48  KW-hours.  Consequently, 
the  activity  of  the  battery,  assuming  no 
loss,  by  very  rapid  discharging,  would  be 
8  KW  maintained  for  six  hours,  or  12 
KW  maintained  for  four  hours.  Of  this 
power  some  will  necessarily  be  lost  in  the 
motors  and  gears,  so  that,  perhaps,  only 
about  75  per  cent,  may  be  available  at  the 
car  axles. 


320 


ELECTRIC   STREET   RAILWAYS. 


Fig.  147  shows  diagrammatically  the 
connections  obtained  in  the  different  posi- 
tions of  the  controller  of  this  car.  In  posi- 
tion 1,  the  two  batteries  are  placed  in 
parallel,  making  an  effective  E.  M.  F.  of  60 


FIG.  147.— CONTROLLER  POSITIONS. 

volts  at  main  terminals,  while  the  two 
motors  are  in  series,  each  motor  receiving 
30  volts.  If  under  these  conditions,  the 
activity  of  the  battery  is  12  KW,  the  cur- 
rent strength  received  by  the  two  motors 


in  series  will  be 


12,000 
60 


=  200  amperes. 


STORAGE  BATTERY  SYSTEMS.     321 

In  the  second  position,  a  shunt  is  thrown 
around  the  field  magnets  of  the  motors, 
thereby  diminishing  their  magnetic  power, 
and  requiring  a  greater  speed  from  the 
armatures  in  order  to  develop  the  neces- 
sary C.  E.  M.  F.  of  60  volts  in  all. 

In  the  third  position,  the  two  batteries 
are  thrown  in  series,  representing  a  total 
E.  M.  F.  available  at  terminals  of  120 
volts,  and  a  corresponding  increase  in  the 
speed  of  the  unshunted  motors  to  produce 
this  C.  E.  M.  F. 

In  the  fourth  position,  a  shunt  is  again 
thrown  around  the  field  magnets  of  the 
two  motors,  and  their  speed  is  correspond- 
ingly increased. 

In  the  fifth  position,  the  two  unshunted 
motors  are  thrown  in  parallel,  instead  of  in 


322  ELECTRIC   STREET  RAILWAYS. 

.series,  thus  calling  upon  each  motor  to  de- 
velop a  total  C.  E.  M.  F.  of  120  volts. 

In  the  sixth  and  last  position,  the  mag- 
nets of  the  motors  are  shunted,  requiring 
the  armatures  to  run  faster  in  order  to  pro- 
duce 120  volts  total  C.  E.  M.  F.  in  the 
motor  under  these  conditions. 

When  the  car  returns  to  the  car  house 
and  the  battery  has  been  sufficiently  dis- 
charged, it  is  lifted  bodily  from  the  truck 
and  replaced  by  a  charged  battery. 


OP  THE       ^X 

TJNIVERSITT) 

-  -^ 


CHAPTER  XVI. 

ELECTEIC    LOCOMOTIVES. 

WITHIN  large  cities,  municipal  ordinances 
generally  limit  the  speed  of  street  cars  to 
about  eight  miles  per  hour.  In  suburban 
districts,  however,  a  speed  is  usually  per- 
mitted as  high  as  fifteen  miles  per  hour, 
while  in  inter-urban  traffic,  speeds  of  thirty 
miles  per  hour  or  more  are  sometimes 
reached.  As  the  velocity  of  the  cars  in- 
crease, the  electric  activity  which  must  be 
supplied  to  them  increases  in  nearly  the 
same  proportion  ;  for,  the  torque  exerted  by 
the  motors  on  a  given  gradient  remains 
nearly  the  same  at  all  the  above  men- 
tioned speeds,  the  rate  only  varying  at 
which  that  torque  is  exerted. 


824  ELECTRIC   STREET   RAILWAYS. 

At  still  higher  speeds  than  the  preced- 
ing, the  friction  between  axles  arid  journals, 
and  the  wheels  and  the  track,  does  not  sen- 
sibly increase,  but  the  friction  between  the 
surface  of  the  car  and  the  air  does  sensibly 
increase,  so  that,  at  speeds  above  100  miles 
per  hour,  the  track  and  journal  friction 
would  probably  commence  to  be  small 
compared  with  the  resistance  to  air  dis- 
placement and  friction.  Consequently,  for 
very  high  speeds,  the  form  of  the  moving 
car  becomes  nearly  as  important  as  the  form 
of  the  hull  of  a  steamer ;  only  in  the  case 
of  the  latter,  the  hull  only  is  exposed  to  the 
friction  against  the  water,  while  in  the  case 
of  the  car,  the  entire  surface  is  moved 
through  the  air. 

The  question  has  often  arisen  as  to  the 
early  probability  of  replacing  steam  pro- 
pulsion on  ordinary  railroads  by  electric 


ELECTRIC   LOCOMOTIVES.  325 

propulsion.  The  schedule  speeds  of  ex- 
press trains  on  steam  roads  have  altered  but 
little  during  the  last  twenty  years,  judg- 
ing from  an  inspection  of  railroad  time 
tables  included  in  that  period.  There  is 
no  doubt,  however,  that  the  introduction 
of  the  electric  locomotive  would  permit 
much  higher  speeds  to  be  safely  attained, 
and,  when  this  fact  is  taken  in  connection 
with  the  manifest  advantages  possessed  by 
electric  propulsion,  it  would  seem  that  in 
electricity,  steam  has  a  formidable  rival  in 
this  field.  The  question,  however,  is  one  of 
public  demand,  and  economy  of  transpor- 
tation. There  can  be  no  doubt,  that  so  far 
as  regards  economy  in  long-distance  trans- 
portation, steam  propulsion  is  cheaper  than 
electric  propulsion,  owing  to  the  cost  of  the 
plant,  since  the  cost  of  transmitting  power 
electrically  increases  rapidly  with  the  dis- 
tance. Consequently,  for  freight  and  slow 


326  ELECTRIC    STREET   RAILWAYS. 

traffic,  it  does  not  seem  that  the  immediate 
future  will  witness  the  displacement  of  the 
steam  locomotive,  but  for  high-speed  pas- 
senger transportation,  the  extra  cost  of  the 
electric  equipment  may  be  repaid  by  the 
increased  economy  in  time  of  transit,  so 
that  it  does  not  seem  improbable  that  in 
the  near  future  the  high-speed  passenger 
locomotive  may  come  into  use  on  railroads. 

As  an  example  of  experiments  which 
have  been  tried  in  the  direction  of  high- 
speed electric  railroads,  we  may  mention 
the  bicycle  railroad  shown  in  Fig.  148. 
Here  the  car  runs  on  a  single  rail  and  rests 
on  two  wheels,  which,  instead  of  being 
placed  side  by  side,  as  in  the  ordinary 
truck,  are  in  the  same  plane,  like  a  bicycle, 
one  being  placed  in  the  front  and  the  other 
in  the  rear.  The  ends  of  the  car  are  tap- 
ered, as  shown.  To  prevent  the  car  from 


328  ELECTRIC   STREET   BAILWAYS. 

falling  sideways  when  at  rest,  it  is  sup- 
ported by  guide  wheels  pressing  upon  the 
upper  or  guide  rail,  which  serves  the  double 


FIG.  149. — SECTION  OF  BICYCLE  CAB. 

purpose  of  a  support  and  an  electric 
conductor.  A  cross-section  of  a  double 
deck  car  is  shown  in  Fig.  149.  It  will  be 
seen  that  these  cars  are  only  of  half  width, 


ELECTEIC   LOCOMOTIVES.  329 

two  being  able  to  pass  each,  other  with  nine 
inches  clearance  within  the  space  occupied 
by  an  ordinary  4'  8  1/2"  track.  The  ad- 
vantage claimed  for  this  construction  is 
that  it  not  only  enables  the  traffic  to  be 
doubled  upon  any  existing  railroad  by 
erecting  the  upper  or  trolley  guides,  one 
for  each  existing  rail,  but  it  also  enables 
the  weight  of  the  cars  to  be  materially 
reduced,  since  the  narrow  car  enables 
the  necessary  structural  strength  to  be 
obtained  with  less  material,  and  the 
weight  of  the  loaded  car,  per  passenger 
carried,  would  be  about  four  times  less  than 
with  the  existing  construction,  thus  econo- 
mizing in  activity  expended  against  journal 
friction  and  grades.  The  electric  propul- 
sion is  obtained  from  a  single  motor  M,  in 
the  front  wheel  of  the  car.  On  the  track 
shown  in  the  figure,  speeds  of  45  miles  per 
hour  are  readily  obtained,  and  speeds  of 


330          BLEOTUIO   8TKEIST   RAILWAYS. 

over  60  miles  an  hour  are  claimed  to  have 
been  reached  on  a  track  1  1/2  miles  in 
length.  By  giving  a  lean  to  the  upper  or 
guide  rail  no  difficulty  has  been  found  in 
going  around  sharp  curves,  since  no  appre- 
ciable strain  is  produced.  A  disadvantage 
of  the  system  is  that  it  can  only  provide 
seats  for  two  in  the  width  of  the  car. 

Another  purpose  to  which  the  electric 
locomotive  has  already  been  applied  is  to 
the  drawing  of  trains  of  cars  through  long 
tunnels  on  steam  roads.  As  is  well 
known  considerable  difficulty  is  experi- 
enced in  ventilating  long  tunnels  when 
steam  locomotives  pass  tli rough  them  fre- 
quently. This  difficulty  is  entirely  over- 
come by  the  use  of  the  electric  locomotive. 
Here  the  requirements  are  not  for  high 
speed,  but  for  a  powerful  draw-bar  pull. 
An  example  of  this  type  of  electric  loco- 


LOCOMOTIVES.  331 

motive  is  seen  in  the  licit  Line  Tunnel  at 
I>a.llimore.  This  tunnel  is  about  u  mile 
Mild  a  luilf  loni;1,  Mild  has  a  ^radicnt  of 
about,  forty-two  feet  to  the  mile.  Since 
the  freight  trallic.  is  heavy,  a  powerful 
hx'oniolix c  is  ivipiiivd  to  dnivv  th(^  tr.'iins. 
I^ig.  ir>()  shows  th(5  eiitr;i.n<T  to  I  lie  tunnel 
with  the  electric  overhead  conductors  (\ 
(',  in  pl,'K5(i.  One  of  th(^se  conductors  is 
provided  for  e.'ich  of  the  two  tnicks.  <u\ 
tt\  nre  the  copper  supj)ly  wires,  und  /if,  K, 
.•ire  tin-  supporting  catenaries  or  rod 
chains, 

Kii;\  lf)l  shows  OIK'  of  the  conductor  sup- 
ports from  the.  cM.tciiM.i-y.  r,  v,  ju-e  the  rods 
of  the  cM.t.c.nary.  /,  is  t  he  conie;il  iusuhitor. 
//,  //,  (,he,  suspension  i-ods  From  this  insu- 
l.-itor.  A',  />',  is  the  IJCMIU  supported  by 
these  rods,  and  < ',  (\  I  he  conductoi's  \\hich 
are  formed  <>!'  iron  bars,  arnin;j;ed  o[»posit,e 


332  ELECTRIC   STREET   RAILWAYS. 


FIG.  150.— THE  ENTRANCE  TO  THE  TUNNEL. 


ELECTRIC    LOCOMOTIVES. 


333 


each  other,  so  as  to  leave  a  slot  between 
them  and  enclose  an  inverted  conduit.  In 
this  conduit  slides  a  brass  shoe  supported 


FIG.  151. — OVERHEAD  CONDUCTOR  SUPPORT. 

on  a  flexible  rod  from  the  top  of  the  loco- 
motive. Wj  is  a  cross-section  of  the  sup- 
ply wires  or  feeders,  which  are  stranded 


334          ELECTRIC   STREET   RAILWAYS. 

copper  cables  about  one  inch  in  diameter 
clamped  directly  to  the  beam  as  shown. 

The  method  of  supporting  the  conduct- 
ors in  the  tunnel  is  shown  in  Fig.  152. 
Here  M,  M,  M,  is  the  masonry  arch  of 
the  top  of  the  tunnel,  B,  B,  are  bolts  let 


FIG.  152.— METHOD  OP  SUPPORTING  CONDUCTORS  IN  THE 
TUNNEL. 

into  the  masonry,  and  supporting  a  chan- 
nel frame  by  two  conical  insulators  i,  i, 
at  the  ends.  Two  other  insulators  if,  ir, 
support  the  conductors  c,  c. 

Fig.  153  shows  the  electric  locomotive 
pulling  a  steam  locomotive  and  train 
through  the  tunnel.  F,  F,  is  the  flexible 


336  ELECTRIC   STREET   RAILWAYS. 

conductor  corresponding  to  the  trolley  pole 
of  an  ordinary  street  car,  and  carrying  at 
its  extremity  the  shoe  running  in  the  con- 
ductor overhead.  An  end  view  of  the 
locomotive  is  shown  in  Fig,  154.  The 
trolley  fastened  to  the  top  of  the  locomo- 
tive is  shown  in  side  and  end  view  at  Fig. 
155.  S,  is  the  shoe,  and  c/,  t/J  the  joints  in 
the  structure,  which  automatically  lengthen 
and  shorten  the  trolley  pole  to  conform 
with  the  varying  height  of  the  trolley  con- 
ductor. This  locomotive  weighs  ninety- 
six  short  tons  in  all,  and  is  supported  on 
two  trucks  and  four  pairs  of  driving 
wheels.  A  motor  is  mounted  directly 
on  each  driving  axle,  thus  placing  four 
motors  in  the  locomotive.  One  of 
these  motors  is  shown  in  Fig.  156. 
Here  the  iron-clad  armature  A,  A,  is 
mounted  in  a  sextipolar  field  frame  F,  F. 
These  motors  being  mounted  on  the  driv- 


ELECTRIC    LOCOMOTIVES.  337 


FIG.  154. — END  VIEW  OF  ELECTRIC  LOCOMOTIVE. 


338          ELECTRIC   STREET   RAILWAYS. 

ing  axles  through  special  flexible  connec- 
tions without  the  intervention  of  gears,  are 
called  gearless  motors.  The  method  of 
mounting  them  in  the  truck  is  shown  in 


FIG.  155.— SIDE  AND  END  VIEWS  OF  TROLLEY. 

Fig.  157.  Here  S,  S,  is  the  side  frame 
c/J  J,  are  the  journal  boxes  of  the  two 
axles  in  the  truck,  and  M,  M,  the  motors 
mounted  flexibly  over  each  axle. 


ELECTRIC  LOCOMOTIVES. 


339 


The  current  is  supplied  to  each  motor 
armature    through    six     pairs    of    carbon 


FIG.  156. — MOTOR  OF  ELECTRIC  LOCOMOTIVE. 

brushes  arranged  around  the  periphery  of 
the  commutator.  The  total  current  sup- 
plied to  each  motor  is  normally  about  500 


340 


ELECTRIC   STREET   RAILWAYS. 


amperes  at  full  load.  The  pressure  of  sup- 
ply is  about  600  volts.  The  normal 
activity  absorbed  by  each  motor  at  full 
load  is,  therefore,  300  KW,  or,  roughly, 
about  400  HP.  Since  there  are  four 
motors,  this  powerful  locomotive  absorbs 


FIG.  157. — TRUCK,  SHOWING  MOTORS  IN  POSITION. 

a  total  activity  of  about  1,600  HP,  and 
the  locomotive  is  rated  at  1,500  HP.  The 
locomotive  is  designed  so  as  to  exert  a 
steady  pull  of  40,000  pounds,  or  20  short 
tons,  at  the  draw  bar  when  drawing  a  train 
twelve  miles  per  hour.  This  represents 
a  useful  activity  of  1,280  HP  in  addition 


ELECTRIC   LOCOMOTIVES. 


341 


to  that  required  to  move  the  locomotive 
itself.  The  maximum  available  draw-bar 
pull  is  stated  to  be  60,000  pounds.  The 


FIG.  158.— "TERRAPIN  BACK"  ELECTRIC  MINING 
LOCOMOTIVE. 

draw-bar  pull  in  an  electric  locomotive  is 
uniform,  whereas  the  draw-bar  pull  in  the 
steam  locomotive  is  necessarily  variable  at 
different  portions  of  the  stroke.  The 


342          ELECTRIC   STREET   RAILWAYS. 

draw-bar  pull  of  a  powerful  60  short- 
ton  steam  engine  does  not  usually  exceed 
25,000  pounds. 

Electric  traction  has  recently  been 
adopted  on  two  short  branches  of  road  in 
connection  with  steam  railroads.  These 
are  at  Nantasket  Beach,  Mass.,  and  Mount 
Holly,  N.  J.  The  road  between  Mount 
Holly  and  Burlington  is  about  seven  miles 
long,  and  is  operated  by  electric  cars 
equipped  with  100  HP  motors;  the  speed 
being  about  thirty  miles  an  hour,  and 
the  schedule  time  for  the  trip  twenty-one 
minutes,  including  stops.  It  is  not  at  all 
improbable  that  this  is  but  the  beginning 
of  an  extensive  use  of  electric  traction  for 
suburban  traffic,  in  connection  with  steam 
railroads. 

The    electric   locomotive    has    recently 


ELECTRIC   LOCOMOTIVES.  343 

found  a  field  of  application  in  mining 
operations.  It  is  especially  fitted  for  such 
work  from  the  ease  with  which  it  is  con- 
trolled. Fig.  158  shows  a  form  of  mining 
locomotive  suitable  for  hauling  trains  of 
trucks  through  the  galleries  of  a  mine. 
It  will  be  noticed  that  the  trolley  pole  is 
of  the  same  general  type  as  that  described 
in  connection  with  the  locomotive  of  the 
Baltimore  tunnel. 


THE 


INDEX. 


Active  Coil,  80. 

Coil,  Deflection  of,  by  Electromagnet,  85. 

Coil,  Deflection   of,  by  Horseshoe  Magnet, 

84. 
Coil,  Deflection   of,   by  Opposite  Magnet 

Poles,  83. 
Coil,  Deflection  of,  by  Single  Magnet  Pole, 

82. 

Active  Conductor,  80. 
Activity,  International  Unit  of,  23. 

,  Practical  International  Unit  of,  24. 

— ,  Unit  of,  21. 
Acute-Angle  Crossing,  240. 
Ammeter  for  Railway  Generator  Switchboard,  263. 

for  Railway  Switchboard,  272  to  274. 

Ampere,  28. 

Analogy  between  Liquid  and  Electric  Flow,  3  to  7. 
345 


346  INDEX. 

Anchored  Filament  for  Electric  Street  Car  Lamp, 

138. 

Anchor-Strain  Ear,  234. 
Armature  Coils  of  Car  Motor,  72. 

Core,  Lamination  of,  74. 

—  Core,  of  Car  Motor,  72. 

,  Cylinder,  75. 

Pinion,  115  to  117. 

,  Ring,  75. 

Windings  of  Car  Motor,  72. 

Arrester,  Lightning,  201  to  203,  266. 
Automatic  Car  Switch,  129. 
Circuit-Breaker,  265. 

-  Cut-Out,  198. 

-  Ear,  233. 

Feeder  Circuit-Breaker,  266. 

Axle  Gears,  116. 


B 

Back  Electric  Pressure,  47. 

Water  Pressure,  45. 

Bars  of  Commutator,  77. 
Base,  Trolley,  205. 
Belt-Driven  Generator,  297. 

Berlin  Industrial  Exhibition  of  J79,  Electric  Rail- 
way of,  12. 


INDEX.  347 

Bicycle  Railroad,  326  to  330. 
Block,  Fuse,  198. 
Blow-Out,  Magnetic,  160. 
Bond,  Welded  Rail,  248. 
Bonding  of  Rails,  245,  246. 
Bonds,  Rail,  246. 
Box,  Sand,  131,  132. 
Boxes,  Journal,  104. 

,  Rheostat,  265. 

Bracket  Pole  for  Double  Track,  221. 

Support  for  Single  Track,  222. 

Suspension  Ear,  231. 

Suspension  for  Single  Track,  223. 

Brackets,  219. 
Brake  Handle,  122. 

Mechanism,  122. 

Shoes,  99. 

Breaker,  Automatic  Circuit,  265. 
Broken  Circuit,  27. 
Bus-Bars,  Generator,  278. 
By-Path  or  Shunt,  182. 


c 

Canopy  Switch,  199,  200. 

Car  Body,  97. 

Brake,  Electric,  126  to  128. 


348  INDEX. 

Car  Brake,  Pneumatic,  122. 

Controller,  Definition  of,  155. 

-  Controller  for    Storage    Battery   System, 

320  to  322. 
Controller,   Interior   Construction   of,  158, 

159. 
Controller,  Method  of  Operation  of,  162  to 

191. 

Heater,  Heating  Coils  of,  144,  145. 

Heating,  Temperature-Regulating   Switch 

for,  147  to  151. 
Lamp,  136,  137. 

-  Lamps,  Circuit  of,  135. 
Lamps,  Efficiency  of,  138. 

-  Lamps,  Fixtures  for,  139,  140. 

-  Mile,  301. 

-  Motor,  Armature  Core  of,  72. 

Motor,  Armature  Windings  of,  72. 

Motor,  Commutator  of,  72. 

-  Motors,  Gear  Wheels  of,  69. 

-  Truck,  67,  68,  97. 

-  Trucks  and  Cars,  97  to  133. 

Trucks,  Methods  of  Supporting,  97,  98. 

-  Trucks,  Storage  Battery,  317. 

Wheels,  Closed,  110. 

Wheels,  Gearing  for,  113. 

Wheels,  Open,  108. 


INDEX.  349 

Car  Wheels,  Skidding  of,  129. 

Wheels,  Tread  of,  109. 

Cars  and  Car  Trucks,  97  to  133. 

,  Electric  Lighting  and  Heating  of,  134  to 

153. 
Carbon-Plate  Automatic  Circuit-Breaker,  267,268, 

269. 
Cell,  Secondary,  309. 

,  Storage,  309. 

Chicago  State  Fair,  Street  Car  Line  of  '84,  14. 

-  Rail  Bond,  246. 
Circuit-Breaker,    Carbon-Plate     Automatic,    267, 

268,  269. 

Breaker,  Magnetic,  269  to  272. 

Breakers,  Automatic  Feeder,  266. 

,  Broken,  27. 

-,  Closed,  27. 

,  Electric,  27. 

,  Hydraulic,  30, 31. 

,  Made.  27. 

,  Open,  27. 

or  Line,  Drop  in,  54. 

Climbers,  Pole,  224. 
Clamp,  Splicing  Ear,  233. 
Closed  Car  Wheels,  110. 

Circuit,  27. 

Coil,  Active,  80. 


350  INDEX. 

Coils,  Armature,  of  Car  Motor,  72. 
Collecting  Brushes  of  Generator,  282. 
Commutator  of  Car  Motor,  72. 

of  Generator,  285. 

Segments,  77. 

—  Strip,  77. 

Compound- Wound  Generator,  280. 
Conductance,  40. 
Conducting    Wires,     Resistance  of,    to    Electric 

Flow,  34. 

Conductor,  Active,  80. 
Conductors,  Feeding,  64. 
Conduit  Trolley  System,  306. 
Coney  Island,  Street  Car  Line  of  '84,  14. 
Consequent  Magnet  Poles,  90. 
Continuous  Rail,  248. 
Controller,    Diagram    of   Connections    for   First 

Working  Notch,  164. 
Controllers  and  Switches,  154  to  203. 
Corrosion,  Electrolytic,  250. 
Coulomb,  48. 
Counter-Electromotive  Force,  45,  47. 

Electromotive  Force  of  Rotation,  166. 

Electromotive  Force  of  Self -Induction,  165. 

Crossing,  Right-Angle,  240. 

,  Acute-Angle,  240. 

,  Trolley,  239. 


INDEX.  351 


Current,  Electric,  28. 

,  Electric,  Unit  of,  28. 

Currents,  Eddy,  74. 
Cut-Out,  141. 

,  Automatic,  198. 

Cylinder  Armature,  75. 

D 

Davenport,  8. 

Davidson,  8. 

Decomposition,  Electrolytic,  250. 

Diagram  of  Load,  299. 

Direct-Driven  Generator,  279. 

Double-Curve  Suspension,  229. 

Gear  Wheels,  119. 

Pinion,  119. 

Reduction  Motors,  118. 

Track  Bracket  Pole,  221. 

—  Truck,  99. 

Dr.  Ohm,  35. 

Drop  in  Line  or  Circuit,  54. 

E 

E.  M.  F.,  29. 

Ear,  Anchor-Strain,  234. 
,  Automatic,  233. 


352  INDEX. 

Ear,  Bracket-Suspension,  231. 

Clamp,  Splicing,  233. 

,  Splicing,  232. 

Eddy  Currents,  74. 

Edison,  13. 

Efficiency  of  Car  Lamps,  138. 

of  Line  Circuit,  59  to  63. 

of  Motor  or  Generator,  57  to  59. 

of  Motor  or  Generator,  Effect  of  Load  on, 

58,  59. 

Effective  Pressure,  47. 
Eighth  Working  Notch,  Diagram  of  Connections 

of,  188. 
Electric  Car  Brake,  126  to  128. 

Car  Heaters,  Advantages  of,  143,  144. 

Car,  Weight  of,  298. 

Circuit,  27. 

Current,  28. 

Current,  Unit  of,  28. 

Gradient,  46. 

Lighting  and  Heating  of  Cars,  134  to  153. 

Street   Car  Lines    of   the   United   States, 

Statistics  of,  14. 

Locomotive,  Motor  of,  339. 

Locomotives,  323  to  342. 

Locomotives  of  the  Baltimore  Tunnel,  330, 

331. 


INDEX.  853 

Electric  Mining  Locomotive,  341. 

Motor,  67. 

Railroad  System,  Self-Contained,  307. 

Resistance,  34,  35. 

Snow-Sweeper,  303,  304. 

Electricity,  Quantity  of,  42. 
Electrolysis,  249  to  261. 
Electrolytic  Corrosion,  250. 

Decomposition,  250. 

Electromagnetic  Pull,  84. 

Twist,  84. 

Electromotive  Force,  29. 
Elementary  Electrical  Principles,  16  to  66. 
Elements  of  Storage  Cell,  309. 
Emergency  Switch,  156. 


F 

Farmer,  10. 
Feeder  Panels,  263. 

System,  65. 

Feeders,  64. 

Feeding  Conductors,  64. 

Points,  65. 

Field,  13, 

Magnet    Coils,    Effect    of    Shunting,    on 

Motor  Speed,  183,  184 


354  INDEX. 

Filaments,  Anchored,  for  Car  Lamps,  138. 

,  Non-Vibrating,  for  Car  Lamps,  138. 

Fixtures  for  Car  Lamps,  139,  140. 

Flattening  of  Wheels,  131. 

Flow,  Electric,  28. 

,  Electric  and  Liquid,  Analogy  between,  3 

to  7. 

Foot-Pound,  18. 

Pound-per-Second,  21. 

Force,  Counter- Watermotive,  45. 

,  Counter-Electromotive,  47. 

,  Electromotive,  29,  31. 

,  Electromotive,  Unit  of,  32. 

Four-Pole  Electric  Motor,  88. 

Fourth  Working  Notch  of  Car  Controller,  Dia- 
gram of  Connections  of,  183. 

Frog,  Left-Hand,  239. 

,  Right-Hand,  239. 

,  Three- Way,  239. 

,  Two- Way,  237. 

Fuse  Block,  198. 

,  Safety,  198. 

G 

Gear  Covers,  120. 

Wheel,  Double,  119. 


INDEX.  355 


Gear  Wheels  of  Car  Motors,  69. 
Gears,  Axle,  116. 
Gearing  for  Car  Wheels,  113. 
Generator,  Belt-Driven,  279. 

Bus-Bars,  278. 

,  Collecting  Brushes  of,  282. 

,  Commutator  of,  285. 

,  Compound- Wound,  280. 

,  Direct-Driven,  279. 

,  Efficiency  of,  57  to  59. 

,  Laminated  Core  of,  285. 


—  Rooms  of  Power  House,  Illustrations  of, 

288  to  294. 

—  Switches,  265. 


Generators  and  Power  House,  279  to  296. 
Gradient,  Electric,  46. 

,  Hydraulic,  44. 

Green,  11. 

Grid  or  Frame  of  Storage  Cell,  314. 

Guard-Wire  Span,  225. 

Wires,  225. 

Wires,  Running,  225. 

H 

Hand  Brake  Mechanism,  123  to  125. 

Heaters,  Electric,  Car,  Advantages  of,  143,  144. 


356  INDEX. 

Heating  and  Lighting  of  Cars,  134  to  153. 

Coils  of  Car  Heater,  144,  145. 

Horse-Power,  22. 
Horseshoe  Magnet  Core,  84. 
Hydraulic  Circuit,  30,  31. 
Gradient,  44. 


Insulators,  Strain,  235. 

,  Trolley  Wire,  235. 

International  Unit  of  Activity,  23. 

j 

Joule,  18. 

per-Second,  23. 

Journal  Boxes,  104. 


Kilowatt,  24. 
Hour,  53. 


Lamination  of  Armature  Core,  74. 
Lamp,  Car,  136,  137. 


INDEX.  357 

Lamp  Circuit  of  Car,  135. 

Lamps,  Pilot,  284. 

Law,  Ohm's,  42. 

Left- Hand  Frog,  239. 

Lever  Brake,  122. 

Lichtenfeld  Railway  Line,  13. 

Lightning  Arrester,  201  to  203. 

Arresters,  266. 

Line  Circuit,  Efficiency  of,  59  to  63. 

or  Circuit,  Drop  in,  54. 

Liquid  and  Electric  Flow,  Analogy  between,  3 
to  7. 

Flow,  Resistance  of,  33. 

Load,  278. 

Diagram,  299. 

,  Effect  of,  on  Efficiency  of  Motor  or  Gene- 
rator, 58,  59. 

Locomotives,  Electric,  323  to  342. 

Lubricating  Bushing  of  Trolley  Wheel,  210,  211. 


M 

Made  Circuit,  27. 

Magnet,  Permanent  Horseshoe,  83. 

Poles,  Consequent,  90. 

Magnetic  Blow-Out,  160. 


358  INDEX. 

Magnetic  Circuit-Breaker,  269  to  272. 
Maintenance  and  Operation,  297  to  306. 
Maximum  Traction  Truck,  100. 
Mechanism  of  Brake,  122. 

— ,  Trolley,  205. 
Meter,  Efficiency  of,  57. 
Milliamperes,  276. 
Mining  Locomotive,  Electric,  341. 
Motor,  Carbon  Brushes  for,  96. 

,  Electric,  67. 

— ,  Electric,  Four-Pole,  88. 

,  Electric,  Quadripolar,  88. 

Load,  170. 

of  Electric  Locomotive,  336. 

,  Street  Car,  67  to  96. 

Suspension,  Method  of,  111  to  114, 

Motors,  Double-Reduction,  118. 

,  Single-Reduction,  117,  118. 

,  Slow-Speed,  118. 


N 

Negative  Plate  of  Storage  Cell,  309. 
Ninth  Working  Notch,  of    Car   Controller,  Dia- 
gram of  Connections  of,  189. 
Non-Vibrating  Filament  for  Car  La^np,  138. 


INDEX.  359 

o 

Ohm,  35. 

,  Practical  Definition  of,  41. 

Ohm's  Law,  42. 

Open  Car  Wheels,  107. 

Circuit,  27. 

Operation  and  Maintenance,  297  to  306. 
Output  of  Station,  299. 

P 

Page,  9. 

Panel,  Pressure,  263. 
Panels,  Feeder,  263. 

Parallel  Connection  of  Street  Cars,  187,  188. 
Permanent  Horseshoe  Magnet,  83. 
Pilot  Lamps,  284. 
Pinion  Armature,  115  to  117. 
— ,  Double,  119. 

,  Rawhide,  120. 

Pinkus,  9. 

Plate  of  Storage  Cell,  309. 
Pneumatic  Car  Brake,  122. 
Points,  Feeding,  65. 
Pole,  32. 

Climbers,  224. 

,  Trolley,  205. 


360  INDEX. 

Port  rush  Electric  Car  Line,  13. 
Positive  Plate  of  Storage  Cell,  309. 
Practical  Definition  of  Ohm,  41. 

. International  Unit  of  Activity,  24, 

Pressure,  Back  Electric,  47. 

,  Back  Water,  45. 

— ,  Effective,  47. 
-  Panel,  263. 
Pull,  Electromagnetic,  84. 


Q 

Quadripolar  Electric  Motor,  88. 

Street  Car  Motor,  91. 

Quantity  of  Electricity,  42. 
,  Unit  of  Electric,  48. 


R 

Radial  Truck,  Action  of,  101. 
Rail  Bond,  246. 

Bond,  Chicago,  246. 

Bond,  Welded,  248. 

,  Bonding  of,  245,  246. 

-,  Continuous,  248. 

Railroad,  Bicycle,  326  to  330. 


INDEX.  361 

Railway,  Electric,  of  Berlin  Industrial  Exhibition 
of  '79,  12. 

Lamp,  136. 

Rate-of-Doing-Work,  20. 

of  Electric  Flow,  28. 

Rawhide  Pinion,  120. 

Resistance  Coil  for  Street  Car,  177. 

,  Electric,  Unit  of,  35. 

of  Conductor,  Influence  of  Cross  Section 

on,  38. 

of  Conductor,  Influence  of  Length  on,  38. 

to  Electric  Flow,  33. 

Wires,  Effect  of  Dimensions  of,  on  Resist- 
ance, 36  to  38. 

Rheostat  Boxes,  265. 

Right- Angle  Crossing,  240. 

Hand  Frog,  239. 

Ring  Armature,  75. 

Robinson  Radial  Truck,  101. 

Rope,  Trolley,  205. 

Rotation,  Counter-Electromotive  Force  of,  166. 

Running  Guard  Wires,  225. 

s 

Safety  Fuse,  11,  198. 
Sand  Box,  131,  132. 


362  INDEX. 

Second  Working  Notch  of  Car  Controller,  Diagram 

of  Connections  of,  179. 
Secondary  Cell,  309. 
Segments,  Commutator,  77. 
Self-Contained  Electric  Railroad  System,  307. 
Self-Induction,   Counter-Electromotive    Force   of, 

165. 

Shunt  or  By-Path,  182. 
Siemens-Halske,  12. 
Single-Curve  Suspension,  229. 

Reduction  Motors,  117,  118. 

Track  Bracket  Support,  222. 

Track  Bracket  Suspension,  223. 

Trolley  System,  204. 

Truck,  98,  99. 

Sixth  Working  Notch  of  Car  Controller,  Diagram 

of  Connections  of,  186. 
Skidding  of  Car  Wheels,  129. 
Sleet-Cutting  Trolley  Wheel,  210. 
Slow-Speed  Motors,  118. 
Snow  Sweeper,  Electric,  303,  304. 
Span  Guard  Wires,  225. 

Wire,  234. 

Wires,  219. 

Wire  Support,  220. 

Wire  System,  220,  221. 

Splicing  Ear,  232. 


INDEX.  363 

Station,  Output  of,  299. 
Stationary  Electric  Motor,  87. 
Storage  Battery  Car  Truck,  317. 

Battery  System,  Car  Controller  for,  320  to 

322. 

Battery  Systems,  307  to  322. 

Cell,  309. 

Cell,  Elements  of,  309. 

Cell,  Negative  Plate  of,  309. 

Cell,  Positive  Plate  of,  309. 

Cells,  Frame  or  Grid  of,  314. 

Straight-Line  Suspension,  227. 

Strain  Insulators,  235. 

Street  Car,  Brush  Holder  for,  95. 

Car  Motor,  67  to  96. 

Car  Quadripolar  Motor,  91. 

Car  Resistance  Coil,  177. 

Street  Cars,  Parallel  Connection  of,  187,  188. 
Strip,  Commutator,  77. 
Support,  Triple-Truck,  101. 
Suspension,  Double-Curve,  229. 

of  Car  Motor,  Method  of,  111  to  114. 

,  Single-Curve,  230. 

,  Straight-Line,  227. 

Switch  and  Cut-Out  for  Car  Lamp,  139  to  141. 

,  Automatic,  for  Car,  129. 

,  Canopy,  199,  200. 


364  INDEX. 

Switch,  Emergency,  156. 

,  Temperature-Regulating,  for  Car  Heater, 

147. 
Switches  and  Controllers,  154  to  203. 

— ,  Feeder,  266. 

Switchboard,  Railway  Generator  Station,262  to  266. 
Switchboards,  262  to  278. 
System,  Feeder,  65. 
,  Single-Trolley,  204. 


Temperature-Regulating  Switch  for  Car  Heater, 

147. 
Tenth  Working  Notch  of  Car  Controller,  Diagram 

of  Connections  of,  190. 
Third  Working  Notch  of  Car  Controller,  Diagram 

of  Connections  of,  182. 
Three-Way  Frog,  239. 
Total-Current  Panel,  263. 
Tower  Wagons,  2,  302. 
Track  Construction,  242  to  248. 

— ,  Double,  99,  100. 
Truck,  Maximum-Traction,  100. 
Tread  of  Car  Wheels,  109. 
Triple  Truck  Support,  101. 
Trolley  Base,  205. 


INDEX.  865 

Trolley  Base,  Boston,  214,  215. 

-  Base,  Forms  of,  213  to  218. 
Crossing,  239. 

-  Ear,  227. 
—  Frog,  237. 

—  Insulator,  227. 

Line  Construction,  219  to  248. 

Mechanism,  205. 

—  Pole,  205. 

-  Rope,  205. 

System,  Conduit,  306. 

System,  Underground,  306. 

Wheel,  205. 

—  Wheel,  Forms  of,  209. 

—  Wheel  and  Harp,  208. 

Wheel,  Lubricating  Bushing  of,  210,  211. 

Wheel,  Sleet-Cutting,  210. 

Wire  Insulators,  235. 

Trolleys,  204  to  218. 
Truck,  85. 

,  Robinson  Radial,  101. 

Twist,  Electromagnetic,  84. 
Two- Way  Frog,  237. 

u 

Underground  Trolley  System,  306. 
Unit  of  Activity,  21. 


366  INDEX. 

Unit  of  Electric  Current,  28. 

of  Electric  Quantity,  48. 

of  Electromotive  Force,  32. 

of  Resistance,  35. 

of  Work,  53. 

V 

V-Frog,  237. 

Vanderpoele,  13. 

Voltmeter,  54,  263. 

for  Railway  Switchboard,  274  to  275. 

w 

Wagons,  Tower,  302. 

Watermotive  Force,  31. 

Water-pipes,  Resistance  of  Flow  through,  33, 

Watt,  23. 

Watt-hour,  53. 

Watt-hours  of  Storage  Cell,  310. 

Weight  of  Electric  Car,  298. 

Welded  Rail  Bond,  248. 

Wheel,  Trolley,  205. 

Wheels,  Flattening  of,  131. 

,  Tread  of,  109. 

Wire,  Span,  234. 


INDEX. 


367 


Wires,  Guard,  225. 

,  Span,  219. 

Work,  17,  18. 

,  Unit  of,  53. 

,  Units  of,  17. 


Elementary 
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rHIRD  EDITION.     GREA  TL  Y  ENLAR  GED 
A  DICTIONARY  OF 

Electrical  Words,  Terms, 
and  Phrases. 

By  EDWIN  J.  HOUSTON,  Ph.D.  (Princeton). 

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